Once activated, how to play offline

Hi,

the topic almost says it all.

I have successfully activated the game via Steam.

Last week I wanted to play the game on my laptop at a friends place, who hasnt got internet and I wasnt able to because the game (STEAM) required to connect to the internet to start the game.

How or where can I set the options that i can play the game without having to connect to the internet?

Thanks in advance.

Thanks mate