Instructions
Turn on the gaming system with "Modern Warfare 2" inside. On the start screen, navigate to the multiplayer mode by selecting "Multiplayer."
Make sure your Internet connection is working. Sign into Xbox live or the PlayStation network by selecting "Sign in." Use your gamertag to get into the network.
Once on the network, select the friends list by pressing either the "Y" or "Triangle" button. A list of friends will appear. Select friends in which you would like to create a game with.
Once your friends are selected, press the "Create lobby" button. This will allow you to chose the type and style of the game. Once inside the lobby, you will be able to chat and work with other players.
After the lobby is created and players are inside, you may select the map in which you want to play on.