That’s a very complicated question, but we’re glad you asked! In fact, helping you answer that question is really our mission here.
The best way to learn how to do something is simply to start doing! The website you’re on now, learn.gamesalad.com, is designed to help you learn how to become a game developer (or how to become a better game developer) through learning by doing.
Our suggestion is to begin with the Your First Game course and then move onto more sophisticated courses as your understanding and mastery grows.