Your first step is to get you somebody who can personally teach you how to play the organ. There are so many buttons and drawbars on there that if you don't got somebody there to help you, then u might not get very far.
Also, I would suggest learning more about music theory. You should know about things like scales, progressions, chords, etc. If you don't learn your music theory, then it's gonna be a real struggle learning the keyboard or organ.
I also suggest learning how to play in every key cuz an organ don't got no transpose button. If all you can play in is C, good luck trying to carry a service in just one key w/no transpose button. You know how church folks is, they can't never stay in one key, they always go to the very key that you don't know that well.