As expressed before me, the chakras are generally the visualization of the ways that the energy of the universe flows through us. Exploring them may help with magic, meditation, and so forth, but but honestly the reverse is far more true.
Meditation is more an act of deep thought. It can involve energy and the like, but it is more an act of contemplation, focus, and will. You use it to learn of yourself and the world around you... the chakras included. Understanding the flow of things, the flow of energy, and how it all interacts with yourself, your emotions, and your will... That is magic. There are many paths to this, and not all of them need involve the chakras or meditation. Some traditions use prayer and folk traditions without this popular New Age spin on Hindu lore.
As to how we use the chakras? We use the chakras in everything they do. As said, they are how energy flows through and from us. And in everything we do there is energy. In physical action, in thought, in feeling, in exerting will... All of this is a manifestation of energy to some degree or another. The limits are really the extent of what nature allows. That isn't to say that the seven chakras are the absolute maximum.
Many people discuss many other similar energy points on the body, but the basic seven are the "main" chakras that are discussed.
Additionally, I would add that there is no need to find your element. Discovering your element is a very modern thing, and I would hazard to say that it is somewhat false. In the past, people were associated with elements based upon their behavior, personalities, astrological signs, etc. This almost never left them exclusively described by a single element.
The reason for this is simply that the elements are never really found isolated. Fire requires air and fuel (earth) to exist. Air blows sand and dust, and carries clouds of rain, or manifests the lightning that burns like fire. Earth is barren without water, air, and warmth to give it life. Water is the glue that holds it all together, and as such almost always contains sediments, minerals, and nevermind the small molecules of air (hydrogen and oxygen) from which it is made. How then are you just one of these? You possess warmth and vigor and passion(fire), you possess thought and imagination (air), you possess substance and strength and form (earth), and all of this is given life by the life blood that pumps through your veins (water).
Just some things I feel too many "new" people are never given the chance to consider.