Things You'll Need
Instructions
Download a mod. Since mods are created by the game's community, they are hosted across a wide variety of filehosting sites, such as FileFront and Strategy Informer. Once downloaded, the mod will be in a compressed format.
Extract the mod with a file extraction program, such as 7-Zip, WinRAR or WinZip, to the game's "Mod" folder, found in the game's install directory. To do this, right-click on the archive (compressed file) and select the "Extract" option, then choose the folder on your hard drive where you have the game --- by default, "C:\Program Files\Activision\Call of Duty 4\Mods\." After you select the folder, press the "OK" button to extract the files to the selected location.
Start "Call of Duty 4" by inserting the game's disc or double-clicking the game's desktop icon.
Click "Multiplayer" from the main menu, and then "Mods." The list of mods you have installed into the "Mod" folder will be displayed. Click on the checkbox beside a mod's name to activate that mod.