First, download and install Stardock Central. It can be found on this website under teh downloads section, it is the means by which Stardock handles thier digital distribution (kinda like Steam, but better).

Once it is installed, go ahead and register. Make sure that when you do so, you use the same e-mail that yo used to order the game.

Now, if you pre-ordered, then you should have recieved an e-mail containing your serial numbers. If Stardock Central does not prompt you to being your download, then you wil have to register your game manually. While in the program click on "Tools" and go to Register Product. Selet what product it is you are registering, and copy and paste your serial number into the designated area.

Once your registration goes through (should just take a couple seconds), you should be good to go!

Thanks Feud and Kryo, I'm downloading as we speak. I had SDC already installed but did not realize I had to manually register the game first and then the download became accessible to me under the "Purchased Software" section (it always just said "Purchase" beside the 'Dark Avatar (Expansion Pack)' option rather than "Install").

Thanks again for your help.