how to mod

hey guys,
im looking for how using mods like zombies, etc, etc...

but im too mauch noob chould someone help me plz?

i downloaded mw2 liberation but i heared that is vac detected.

btw, what is vac chaos?

thank you very much

MW2 Liberation is detected, unless you don't wanna get banned.
Use AlterIW, You're allowed to mod there.
Vac chaos is the old version of Liberation... xD That has been detected since long time ago.

So yeah....