:wave: Welcome to the forum, Anthony
Probably the best method to become a good organist is to obtain the services of a teacher or tutor, someone who is actively in the profession. It's the way most of us learned, and many of us like myself, started out with years of piano lessons as well.
There are also a couple "method of" publications, one by John Stainer and another by Harold Gleason, the latter of which is rather pricey, even for the older out of print editions.
Of course, the bottom line is practice, practice, practice and when you think you're done practicing, practice some more. The rewards are well worth the effort ... I obtained my first church organist position in 1960, and have been playing, and concertizing, ever since.