[SOLVED]How do u use mods in steam?

I was wondering how do u use a mod in steam?

plzz answers

1. what mods?.
2. you might need aiw,
3. legit mw2 dont allow mods = no console = no mods = no fun.
4. peace

Haha legit mw2 does allow mods get a mod loader good disabler and use them