In the manual. See that link on the left menu bar that says 'manual'?
And could you explain CLEARLY what you mean by "evry time i try it wont let me" as I don't know exactly what you're trying, how far you're getting, and what it does that keeps you from doing it. There are any number of things you could mean when saying it that way, and as I'm sure you know humanity hasn't yet evolved to the point where it can read minds or surely you wouldn't need to be here asking.