If I get my own luggage is there a rack to put it on on the bus or does it go underneath?
It goes underneath. The driver will handle it for you, so it's customary to tip him or her - maybe $1 a bag.
When I get to resort then what?
The driver will take it out of the bottom, you will take it from him and tip him, then you roll your luggage into the lobby and check in to your room.