Instructions
Load the "Call of Duty 4: Modern Warfare" game disc in your console or PC and select "Multiplayer."
Select "Find Match" and wait for the game to connect you to a game lobby. A new screen will pop up and the first map in the rotation will appear at the bottom-left.
Select "Vote to Skip" if you don't like the currently selected map. If the majority of players vote to skip that map, another map in the rotation will be selected instead. Once the timer at the top-right of the screen reaches zero, the match will begin; map rotation has now been set up for your multi-player match.