I buyed World of Goo from internet, cause was that birthday offer.

Can i add that game to steam, not like "Add non-steam game"? Would be lot easier to me, thank you already :)

Most likely not. I heard that only the preorder people got a Steam key to use. You can try contacting Valve, but they'll most likely ignore you or tell you that you'll have to buy it on Steam. It's pretty hard to validate orders just based on a download link and a simple email because you can change names and stuff. The Valve people are not going to go out of their way to confirm orders.