For the illiterate, I've created a guide. :)
1. Obtain a config by right clicking on the document and selecting Save As or Save Link As [depending on the browser]

2. Navigate to your Main folder [C:\Program Files\Call of Duty\main]

* When using a config for the
first time, back up your original config by renaming it. Simply add something to the end of its name.
Ex: "config_mp.cfg" to "config_mp1.cfg" in case you decide to return to it at another time.

4. Move your downloaded config file to your main folder

5. While in game, pull down the console with the ~ key and type /exec
configname.cfg
followed by a /vid_restart


6. When you want to swap configs again, repeat the process by downloading a new file,
moving it to your main folder, and executing the filename in console while in game.
7. If you ever decide to return to your original config, delete "config_mp.cfg" from your
main folder and rename "config_mp1.cfg" BACK to "config_mp.cfg"