Go on the USPSA website and read the rules.
When you get to the match tell them upfront you need instruction. The RO of your squad will make sure you are guided all along the way. Take your time shooting. don't turn around with your pistol unholstered.
Don't do anything unless instructed by the RO. watch the direction of the muzzle when reloading. Did I mention take your time?
You are shooting production class? have at least 4 mags. mags can be more than 10 rounds, but you will only be able to load 10, except for mag #1, you can load 11, because you start with a loaded gun in most stages and will still have 10 in the mag. I have been able to complete every stage ive ever shot, except for one time, that I really screwed up and ran out, that cost me 8 misses or 80 points. You can put the mags in your pockets if you don't have all the gear. All you really need is a holster, eyes and ears.
Have fun and be safe.