Someone told me once that the only stupid question is the one you don't ask. Pretty hard to learn without asking questions, and when you're beginning you have to ask beginner questions! That said--I'm not sure how to answer without knowing what kind of begonia you're asking about. Can you post a picture? Some begonias can be propagated from leaves but some can't. What I often do is cut the long stem for propagation and let the new growths coming from the base grow to make a fuller plant--but there again it depends at least somewhat on what kind of begonia. Can you describe it some more if you can't post a picture?