You have to retrieve your checked luggage from the carousel and take it to the bus.
If you bought your air from RCI, or if you bought transfers from RCI, you should have tranportation vouchers in your e-docs or paper docs. They will take those from you as you board the bus. If you qualify for the transfer buses but don't have a voucher, don't worry. They will have your name on the manifest and the bus driver will be able to check you off and let you board. Somebody will be standing at the bus door with the list of approved passengers.
I bought transfers for my Oasis cruise but it was after my docs had been prepared, thus I didn't have vouchers. This is not a problem though, since all I had to do was give my name and the driver checked me off on his list of approved passengers.
In your case there is enough lead time and you will get vouchers.
One more question about the transfer I'm wondering about, even though my cruise is still a ways off.
For my bag that I want to carry on the ship, I assume it's best to have this with me on the bus, as opposed to in the luggage compartment? It will be a duffel bag. I ask this because a friend of mine went on a cruise out of Puerto Rico. They gave all their luggage to the bus driver, and all of it ended up getting checked at the pier.
2007 - Majesty of the Seas
2009 - Enchantment of the Seas
2010 - Freedom of the Seas