How do I use this to
Whats the procedure with Chessmaster 9000 to set up a position from another game I'm playing online, and use chessmaster 9000 to help me find the best next move?
I trust that your game is finished... otherwise, that would be cheating.
Anyway, you have two options... if you have a PGN file, you can just load the game (Select 'Load' from the File menu). But if you don't have a PGN, then you'll need to use the Set Up Position (Select 'Set Up Position' from the Game menu). Then, you set the board exactly as you want it, and then choose the side to move. From there, you should be able to use Quick Hints from the Mentor menu to help you find the best next move.
Hope this helps,