How do we use commands

I was wondering how to use commands i tryed the list but none worked pls show me a screen shot or just explain pls and i will add a thx for u

Open the console, type in a command, hit execute (not enter). Done, try using some of these:Useful commands: changelevel 2 || changelevel 3 - Minesweeper

how do we get the consosle we download it or is it on game?

No offense but your a dumbass (because there is a thread below your with the console, and before you ask NO ITS NOT FKING DETECTED, its Unknown, meaning you could get banned and you could not), here is the thread with the console download:
http://www.mpgh.net/forum/267-vindic...ell_demon.html