Instructions
Select "Multiplayer" from the "Call of Duty 4: Modern Warfare" main menu.
Choose the "Live" or "Online" option from the Multiplayer menu, and select "Private Match."
Select "Game Setup" from the Private Match Lobby screen, and then change the map, mode and rules for the server, if desired.
Click on the "Invite Friends" option at the bottom of the Private Match Lobby screen to invite your friends to join your server. Click "Start Match" to begin playing on your "Call of Duty 4" server.