@OP -- IDPA just shoot it, forget the watch first.
There is a link to the official forums on the IDPA.com web site (bottom)
And to the current / new rule books.
There are a good number of videos on YouTube - including those hosted in ID
so you can get an idea. PowerFactor has a couple of what to expect at your first match videos hosted there.
The current rule book is a bit more complicated than it needs to be, read thru the safety and shooter sections - you can skip the Safety Officer and Match Director sections.
Don't spend too much time trying to memorize it ... there is a New Rule Book for Oct 1st and in reality, most of the rules are learned best by doing - ie - you can get an aneurysm trying to read about a reload with retention vs a tactical reload in the rule book, and the reality is that it just doesn't' matter.
Do check with the hosting facility to find out if you have other rules to comply with - for example, can you conceal carry arriving / leaving the property. Do you have to check in with them. Is there a required safety course.
I see your question on many of the forums around the net, so you can do some searching and get 300 million answers.
My advice is to keep it simple, and shoot. You must be safe with your pistol, it is not a place for training, first time shooters.
And don't kill any kittens ;-)