Select "Multiplayer" and enjoy. You can use the ~ key to open the console and type name [yourname] to change your username. Troubleshooting: Anti-Virus and Errors
You need a clean, base installation of the game you want to play. While some clients can run without it, having the official Steam files is the most stable method. xlabs launcher download
The launcher was designed to manage several specific, heavily modified versions of older Call of Duty titles: Select "Multiplayer" and enjoy