To answer questions about equipment, download the rule book from USPSA.org, assuming the place you will shoot the matches is following US rules.
If they are following IPSC international rules, then go to that web site.
(Can't remember it, right now, but it googles easily).
As for learning how and what to do, that requires training to be safe with holster draws, reloading on the clock and moving with a loaded gun.
If you are comfortable doing this, just go to a match and let them know it's your first.
Most clubs will squad you with someone experienced in being with new folks.
If the above is uncomfortable or intimidating, there are other similar type matches that don't require movement during the course of fire or reloading on the clock.
NRA Action Pistol and Steel Challenge come to mind.
They are both excellent places to start, if there are any in your area.
Either way, enjoy yourself, be safe, have fun and learn.
Oh yes, bring lots of ammo.