in game server?!? whats that?!? if you mean the console you need to go to the main menu, into settings and then ADVANCED... on the right of the screen is a box that says CONSOLE, put a tick in it by clicking then click APPLY and go into your game...
to use this in the game just press the key next to number 1 (under esc key) this is called the tilde key, and from there you can type in all kinds of stupid things to break your game so try to be sensible when you use it
