JustSayin: You don't need to download it fully (if at all). I still have the LFD 2 freebie and I haven't touched it yet. People are saying to be safe, start the download then cancel to make sure.
niniendowarrior: While I don't know if you have to download the game in its entirety, definitely need to start the download.
I got it from the website through the browser, and I didn't need to. I clicked INSTALL GAME, and then it said it was associated with my account, and provided 2 buttons, one if I had steam installed, and one if I needed to install steam. I just closed the tab, since I didn't want to install it just then, but it is in my library now.