download it, put the 2 .ff files in a folder inside your Program Files/Activision/Call of Duty 4 Modern Combat/usermaps folder called "mp_kob_breakout".
Put the .iwd file in your Mods/ModWarfare folder.
Launch CoD4, click mods, select ModWarfare.
When it restarts click start new server. I always use team deathmatch, maximim players 1, then I go to Gametype Settings and set the time as unlimited and spectate to free (in case you wanna go spectator mode, then just fly around).
Start the server on any of the stock maps. When it gets loaded hit the ~ key and type /map mp_kob_breakout