Modern warfare 3 Ban

Hi I am playing Modern warfare 3 on steam. And there is thing called Theater which you can save all your videos and replay it.
But its full and i want to delete all of it or i want its location.
So there is a lots of noobs are just hack into it which ruins the game and i goddamn want to report them so what do i have to do to report them on steam? ++++++ i want the saved multiplayer videos location as well
Answer #1
just report the player on steam you wont be the first to report them.
Answer #2
Ste#. replied: just report the player on steam you wont be the first to report them.
How????
Answer #3
https://support.steampowered.com/kb_cat.php?s=40513b215613e6406ce6497346765421&id=10&t=qanda#1010-TOKN-8461