Some traders find reading literature as the easiest way to know basics of margin trading while oters isnist on first-hand experience, you know, to touch these buttons, to open these orders and so on.
If you have never tried either theoretical learning or practical ones, then gradually start reading something in forums, chit-chat with fellow traders, or just pass courses. If you realize that this knowledge slips your mind quickly, then try trading on the demo or on such accounts as Cent one. The latter is more beneficial from the point of emotions control skills honing.