If you go to coloradowhitewater.org and look at the CWWA Training camp, that would be a great way to get started in the sport. You have to get your boat elsewhere (rent one), but I definitely recommend going to training camp. I'm going too!
It's a 2 day training, and I assume you will probably spend the first day (or part of the first day) on flatwater just getting used to maneuvering the boat, flipping over, wet exiting, and rolling. You will probably go on a really easy section of river next, learning how to maneuver your boat in the rapids.
Definitely take a lesson regardless. It's really important to make sure you have a good foundation, because if you start on a river that's too hard, you may hate it and never want to go again (that happened to me!!!! So I know! luckily I stuck with it

). I assume confluence does lessons, and boulder outdoor center in Boulder (
www.boc123.com) has a good kayak school too.
The good thing about the training camp is that CWWA also has lots of group trips for people of all skill levels. So you can go on those too after you join CWWA
See you on the river!