There are 7 "village" stops at CBR, plus a stop at the Custom House, which is the check-in area. Your room will be in one of the villages, which are named after Caribbean islands or countries: Jamaica, Martinique, etc.
To get to a theme park or DS, you just go to the nearest village bus stop and wait for a bus to your destination; no transfer is needed. To get back, just board a CBR bus and stay on until it gets to your stop. Buses come into the resort at 2 different entrances, so your stop may be the 1st one on one trip and the 4th stop on another.
Buses returning to CBR usually make all village stops in the resort, unless it's before 11am or if there are a lot of Guests boarding at the resort and the bus fills up. If a bus fills up before reaching its last stop, and there were Guests on the bus returning to the resort, the driver should ask whether there are Guests destined for one of the remaining stops. If you get on a bus at the resort intending to get off at another stop within the resort, let the driver know just in case it fills up. If you are returning to the resort before 11am, check with the driver that the bus is going to your village.
The 8th stop is the Custom House. Theme park and DS buses do not stop at the Custom House; it is serviced only by the Internal Resort Shuttle. (The ESPN WWoS bus also picks up here.) You can board the Internal Resort Shuttle at any village stop to go to Custom House, or to Old Port Royale where the restaurants and recreation are located. The Custom House is also a very short walk from the Barbados stop. Depending on the time of day and where you are starting from, you may also be able to board a theme park or DS bus to get to Old Port Royale or Barbados; you will need to ask the driver. The same is true returning to your village from OPR.
I think that covers everything you need to know about CBR transportation. Feel free to ask any questions.