I know that some refs come from kickboxing backgrounds, and some from wrestling. A lot of the major guys have their own schools, and all of them are registered with their state athletic commissions.

MMA referreeing is relatively new, and there are lots of them needed.

I attached a link to John McCarthy’s MMA ref training school. There’s some good info, and you can see if you are interested enough to take a course.

Good Luck.