after u move another picture appears...at the bottom it states " conditional moves", click on those words and u get a new game picture--u make a move u think your opponent will make and a response.u can make any number of moves.Theres is a delete and return to game wording at top.If your opponent makes a different move anything u did is erased. good luck !
How do you pre-move on chess.com?

For Online Chess it works exactly as eddysallin has described. For Live Chess you have to enable premoves in your Live Chess Settings. Here are the details:
http://support.chess.com/Knowledgebase/Article/View/109/0/what-are-premoves-and-how-do-they-work
How do you pre-move on chess.com?