Anyone actually know where these items are? I input the code on the receipt and got a download for Darkset Pack, but I can't figure out how to obtain these items. Are they available for campaign playthrough, or do I need to do something to unlock them? Any info would be appreciated.

I have the same things. Once I activated it in the Extras menu I didn't get them until I beat the game and started a new one in Old School. The gear isn't that good. Its a little bit better than the gear you find in the first half of the first chapter, but thats all.