Competing-Where to Start?

I was curious as how one starts competing in bodybuilding competitions. I was recently wondering how having a specefic day to train for might be an added incentive to training/dieting. I’m not talking about competing with Coleman and Cutler or the like, just a way for an amateur to get started.

I have to admit I know very little about this topic. Do you just sign up for an amateur contest? is there some type of screening process?etc. Once again, I apologize for the ignorance