On our last cruise, Palo ressies were in Rockin Bar D. They will be listed on the form that you get when you check in. Dining changes were in Sessions.
Each cabin is allowed one brunch, one dinner, and one tea reservation. There are people who cheat on this--if you are travelling with a group, each cabin can make a ressie for 4 (when there are only 2 adults in the cabin), and go on two nights. On the "day of", if you call, they will give you any open slot that might be left. People frequently cancel, so openings do occur at the last minute. THey also keep a wait list after ressies are filled...
As I said earlier, I've never had a problem getting ressies, but I'm at port by noon (the WDW busses arrive about 1 pm).