You can one of a few things,
take a bus to Magic Kingdom and take the boat to Fort Wilderness ( we did this but make sure you plan on leaving early because it took us about an hour in travel time from AKL to MK to FW) this seems to be the easiest especially if you happen to be at Magic Kingdom that day.
you can call the hotel to see if they do have a bus out there but remember you will probably have to stop at all the other hotels on the route so you'll have to leave extra early
depending on what time your show is and what time magic Kingdom is open until depends on how you get back to your hotel.
if its the early show and Magic kindgom is still open it is easy jump on the boat back to Mk and take the bus back to the hotel
if you have a later show and either Mk is closed already or the boat has stopped then you have to take the internal bus( the buses that just travel though Fort Wilderness) at Fort Wilderness to the external bus stop( the ones that go to the parks and stuff) to catch the bus to Downtown Disney and get your bus to your hotel there. ( which is the only place that has buses still running to all the hotels after the parks close)
We actually got lucky last time we went because there were so many people they sent the external bus to pick us up at the hall instead of having to take the internal bus to external bus stop.
hope i didnt confuse you too much!!!