This game is a little more complicated then Supreme Commander, being a 4X game and all.
Also, for those just starting out on this, some games can last for several hours, sometimes even days depending on the size of the map you pick and how you play.
And for those looking for a key, try right clicking on the game in Impluse (My Games tab) and hitting 'view registration'. Not sure which key this is exactly, as I didn't need one, but it may be the one you're looking for.