I applaud you for thinking about trying something out of your wheel house. Polo is fun, uses a lot of different skills and is challenging for the horse and rider. I grew up with families that had strings of polo ponies that played on teams (in Nashville in summer and Florida in winter - not sure if it was amateur or pro - they were serious players and very good). I was a hot-walker and exercise rider for a few summers for a member of a local team. And got a few lessons along the way - though it was for fun. One family had a polo field on their farm for practice.
So my insight may be limited (as well as outdated - when I was doing this, the balls were wood! LOL). Its takes a good bit of time to become really proficient in polo (unless its the only riding you’re doing, and you’re doing it multiple times a week). It takes a really strong core, a good sense of balance, a really good seat, stamina and quick thinking. But my guess is that they start beginning lessons with basics - the tack, holding the mallet, neck reining, striking the ball at a walk/trot, and of course, basic rules of the game.
I would imagine a large club does hold scrimmages for beginners/novices, assuming they have enough people to fill out teams.
If I were undertaking this endeavor, I think my first stop would be my local book store for a good book on learning polo. Then I’d check on what equipment that I’d need for lessons - special helmet, knee/shin guards, gloves, vest, etc. The club should be able to provide this to you (and maybe the club provides all the needed equipment - just make sure it fits properly). Having the right equipment that fits correctly is very important. Those balls sting when you get whacked with one!!!
I wish you much luck! This sounds like fun. 