Then perhaps you should read the articles on here, read the stickies in the forum, read whatever you can find, and just keep reading. Study, and when you have a specific question, ask. Find people, if you can, that are experienced in this, and talk to them.
Just asking "I want to be able to cast and do magic" really says nothing about what you're wanting to learn.
Read, research, study, practice, repeat. There are good forums here on site. Go the the General Info section of the forums and read through the stickied threads. There are also some good articles. Look through them. Find some books on witchcraft, read them. Do some independent studying. Look up your questions on google. Ask people here. When you have some study and understanding under your belt, practice. But never stop trying to learn new things.
I agree with the posts above before you try to cast a spell its best to learn how to cast it other wise it will be like trying to run while you cant walk. Learning about herbs,candles and intentions and so on is very important when it comes to even casting the simplest of spells. Know what you are doing and why you are doing it. I see allot of people try to cast spells when they dont know the difference between real magic and hollywood magic in movies and trying to learn ways of using energy and so on.