Also, why not ask me directly through steam-chat? :p

(My apologizes for not answering earlier) The commands can be placed anywhere in the config.cfg, as long as it's not touching an already existing line so create a new line (you know... with the enter key). And no, the intels don't have to be collected to play the arcade mode.

You edit the config file by going to your MW2 install folder and then find and open the players folder. After you've found it, you should see a file called config.cfg, open it up and add those lines needed for the arcade mode.