How do I add my Mass Effect 2 to steam games list?

I bought my copy of Mass Effect 2 from a GAME store since my connection isn't very fast to download via Steam (would take ages). Where is my product code (different to product key) located so that I can add it to my Steam games list?How do I add my Mass Effect 2 to steam games list?
Just go to your games list, click "Add Non Steam Game" then when the next window pops up click "Browse..." and then look in the "Program Files/Bioware/Mass Effect 2/" for the .EXE of the game. Simple.