All of the above info is 100% correct, I'm just going to package it differently for you, since all of this seems totally new to you.
CBR has 7 bus stops, one at each village plus one at Old Port Royale, the central complex that has the food court, main pool, etc.
Go to the stop most convenient to you. Buses will come by every so often, and they are clearly labeled. There are buses for each of the 4 theme parks, plus a bus for Down Town Disney. Each bus stops at every stop. The Magic Kingdom bus will by every 20 minutes or so, the Epcot bus will come by every 20 minutes or so, and so on. So, as you stand there, there will be a bus going by every few minutes.
As Lewisc suggested, your best bet will be to catch the bus to Animal Kingdom (AK), and once you get to Animal Kingdom, look for a bus going to AKL. And as Lewisc also suggested, if you elarn from others at your bus stop that a bus bound for AK just left, then rather than waiting another 20 minutes or so you'll be better served to catch a bus to Epcot or MGM (whichever comes first), since both parks are relatively near CBR. Once at that park, find a bus departing for AKL.
You'd do the same for the way back to CBR. However, this will only work for parks that are still open. For instance, AKL tends to close pretty early, around 5:00 p.m. on many days from what I recall. If you're trying to get to AKL at 8:00 p.m., you won't be able to use AK as a bus depot, I wouldn't think.
HAVE FUN!