Welcome to SoM,
Well first thing is first, you must learn how to successfully meditate. Meditation will help you learn focus, it takes many years to learn how to successfully meditate. Focus is one of the main things you need to learn before spell casting.
How To Meditate
If you watch "The Last airbender" you see when he meditates he criss-crosses and meditates like that. You don't necessarly need to do that. You can lay on a bed (On your back) or on a sofa (On you back). You will need to relax your body. Going into a deep hypnotic state. In order to relax you will need to take deep even breathes. Some people inhale from their nose out their mouth each time to the count of ten.
To Cast a Spell
After you have learned the art of meditation, you will have hopefully learned focus. Also you should know that meditation can be used for more then just focus (but that this for a later date). You will also need "Belief" belief in the power and energy that surrounds us is need in order to use it. Without belief ther is nothing. You will also need "Imagination" most people have a imagination of such, but you will need a imagination to see what you want your spell to do and what the outcome of the spell would be. "Emotion" This one is for if you want something that you show emotion for, when you cast your own spells, you can use your own emotion to give your spell the extra energy boost.
There are plenty of forums for beginners, and you can also visit "Newbie Central" which is on the "Home" page. It contains inforamation the basics. You also go onto the "Articles" tab, and click on "Survival Guide" it will help you understand this site more.