Step 1: Visit https://www.gog.com/galaxy
Step 2: Download and install GOG Galaxy.
Step 3: Launch GOG Galaxy, and create GOG account. (Just login if you already have a GOG account.)
Step 4: Login to newly acquired GOG account.
Step 5: Click "GOG" icon at the top left of GOG Galaxy.
Step 6: Select "REDEEM CODE" from the drop down menu.
Step 7: Locate activation key from your delivery email.
Step 8: Enter provided activation key.
Step 9: Complete Captcha verification.
Step 10: Click "CONTINUE".
Step 11: Click "CONTINUE"
Step 12: Select new game from library.
Step 13: Click "INSTALL" to begin game download.
Step 14: After download completes, click "PLAY" to play your game.
We hope this helps, and if you need any further assistance, we have 24/7 support that can be reached via email at email@example.com, via our live chat at gamecheap.net, or by phone at 1-888-507-9992.