Enter your unique product identification code when prompted. This code is usually found on a sticker on the back of your game manual. Select Modern Warfare 2 on the game select window and hit the Next button. Insert the second install disc when the installer asks for it.Once complete, the game will be ready to run.nter your unique product identification code when prompted. This code is usually found on a sticker on the back of your game manual. Select Modern Warfare 2 on the game select window and hit the Next button. Insert the second install disc when the installer asks for it.