The game install is about 1,600MB and then simply boot it up.
You might get a network prompt asking the game to get access which you can simply ignore if you don't choose to actually play the game.
Then upon the actual game screen coming up which should be windowed by default, the achievement should also pop up next to the Steam overlay message.
Now feel free to close out the game in the upper-right corner or select the bottom option on the game screen.
Easy game completion.
Update for 32-bit Windows users.
I've heard that this will not unlock at all for people running this OS variation. No work around exists, you'll simply need to find a 64-bit machine to play on.