Fire: Used for purification and defense, often visualized as red energy; sometimes easier to begin working with that way. I usually see a yellow-orangish colored stuff that 'feels' and looks a lot like fire, though the color red is often associated with it by traditionalists. Fire is thought to be the universal force of expansion.
Water: Healing, cleansing, regeneration, motion/movement, often visualized as blue energy. Again, blue is associated with it traditionally, but my mind represents it differently so that it looks like blue and/or clear watery stuff. Water is thought to be the universal force of contraction.
Air: Intellect; mental stuff, can be used as a force to push something away or draw it near, can also purify by blowing the dust 'out' or 'away' from something etc. (use your imagination here) Often visualized as yellow energy. I see and get more of the feeling of air or breezes when working with it, though I used the color yellow to visualize elemental air when first learning. Air is thought to be the universal force that reconciles Expansion/fire and Contraction/water.
Earth: Solidity, strength, making things permanent, some regenerative capabilities, often visualized as green energy. I think of cool, rich, earth or soil sometimes, but 'green' will work fine until you get more into various aspects of the element. Earth is thought to be the combination of Fire Air and Water, and is the universal force of solidification present in physical manifestation.
Spirit: The element of Spirit (the 5th element), often visualized as White energy (I see just a hint of ultra-violet). Spiritual energy can be used for almost anything. You'll have to work with it for a while to get a feel for it and decide how you wish to make use of it. Some people have a difficult time learning to control energy in this phase. Spirit or 'Akasha' as it is sometimes called, is thought to be the universal life principle underlying all things (the universe and everything in it is 'alive' or conscious to some degree). According to my own channeled info, Spirit is "that which permeates all things."
How to start learning to use them
The easiest way to learn to use and channel these energies is to meditate and try to feel yourself immersed in and filled with each one. If the element you wish to work with is fire, then meditate/relax, and then imagine yourself being filled with fire but not being harmed. Try to feel this strongly. 'Feeling' the physical sensation of each element with your whole body is the most important sensation here - it's not just mental visualization. Try to include smells and tastes (until you can almost smell and taste them mentally) as well as the usual mental imagery. In the case of fire, you might even pretend to inhale the fire into your body to get a good feel for it. Do this often until you can feel yourself filled with each energy type easily.
It is recommended that much time be spent meditating and balancing/purifying the self with each element. Once you are able to 'power up' with an energy, then you can begin to work with very basic methods of putting it to use. Example: If you wished to charge or purify an object or talisman with Water, you would 'power up' with or 'inhale' elemental water, and then 'exhale' or direct it at the object with the intention of either purifying or charging it with that energy type. This is the most basic method of utilizing elemental energy. Use your imagination for the rest.
Note on elemental energy
From my observation, the 4 lower elements of fire, water, air, and earth are all very much like fingers all attached to the same hand (the 'hand' being Spirit). In other words, all energy is virtually the same energy, the same light, just in different phases.
"The four elements of nature: Earth, Air, Fire and Water are the very foundations of creation and the basis of life itself. Ancient myths and theories tell us that Divine Beings 'Spirits' were sent to the fledgling earth (then a smoldering pot of confusion being created), to bring about order out of chaos. As the rays of their celestial bodies made contact with the crystallized influences of the lower world, they became the four elements linking humankind to nature, the heavens and the Divine. "
It is also said that from Akasha, spirit, or Ire, came the four elements. All of the 4 elements together make the spirit of Akasha. Without Akasha, there would be no life in anything. Akasha is considered the 5th element, though in truth, it would be the first. A symbol to represent all five elements, is a pentacle/pentagram, the five pointed star, with one point pointed up. The top point would be Akasha, ,making it the central element, and the rest, the four directions, earth-north, air-east, fire-south, and water-west. The color of Akasha is purple, or clear, no color. Most do not use symbols, but say all symbols represent Akasha, though one popular among those I know use an eye with a tear drop, or an egg(which is also used by others). Ancient Hindus had described Akasha as the omnipresent spiritual power that permeates the universe. Also, many among us believe that Akasha is more than just Spirit, and has a consciousness, and is Mother of the Council of 12. There are many beliefs, but most can agree that Akasha means Spirit.
Earth:Cycles, Fertility, Growth, Life & Death, Mystery, creation, destruction, stability, strength, practicality, patience
Elemental: Gnomes,Dwarfs, Elves, Brownies, Hobgoblins, Fae
Other: Earth is primarily a feminine element, and it is cold and dry.
Air: Intelligence, movement, travel, wisdom, messages, weather, intuition
Elemental: Sylph, faeries/pixies, angels
Other: Air is primarily a masculine element, and it is hot and moiste
Fire: passion, warmth, motivation, blood, anger, sexuality, revenge, destruction, vitality, power, strength, courage and defense
Elementals: Salamander, Jin
Other: Fire is primarily a masculine element, and it is hot and dry
Water: knowledge, flow, emotion, love, illusion. weather, purity, cleansing, clairvoyance
Elemental: Undine, Nymphs, Nixies,Tritons,Merfolk, Sirens
Other: Water is primarily a feminine element, and is cold and moiste
Symbols, tools, and places to help you get in touch with each element are:
Earth: salt, a pentagram, herbs, stones, dirt, trees, plants, mountains, the forest.
Air:feathers, wands, insence, smoke,
Fire:[the sword or athame, candles, torches, light, bonfire, incense, volcanoes, blood, wine.
Water: cauldrons, cup or chalice, lakes, rivers, the ocean, seas, puddles, bowls of water, rainstorms
Magical qualities & influence
It is used to influence such matters as: Female principles, herbal magic, things that are cold and dry, protection, luck, physical healing, balance, prosperity, change, material things, harmony, success. Also used for artistic ability, affection, alliances, grace, luxury, social activity, marriage, family, home protection, gifts, income, and gardening. It is an extremely multi-purpose element.
Light, health, success, careers, goals, ambition, personnel finances, advancement, drama, fun, authority figures, law, crops, totem animals, promotion, male principles, youth, buying, things hot and moist, gales, hurricanes and tornados. Also used for achievement, healing energy, divination, clairvoyance, mental alertness, intelligence, intellectual harmony, energizing, creativity.
Passion, partnerships, action, physical activity, energy, aggression, sex, sports, guns, swords, tools, metals, soldiers, combat, confrontation, war, business deals, buying and selling, mechanical things, repairs, hunting, health, success, ambition, and authority figures.
balance, cleansing, joy, illusion, opportunity, love, elevation, tranquillizing, aligning, logic, gambling, social matters, political power, publishing, education and long distance travel, brooding, foreboding, stagnation, poison, toxic substances, religion, philosophy, expansion, luck, growth, legal matters, research, reading and studying.