I got this one figured out!
I ordered my server with Windows Server 2016 as a secondary OS, so I wasn't expecting it, but they stuck the product key label on the back of the unit. Since it was ordered as a secondary, I was expecting the product key to be on the sleeve of the disk. I also read that if it's a VM the installation media has a key that it uses, which added to the confusion - must have been for something else.
There should be a little blue square that you have to scratch off in order to see the full key, but it's there. Then you just activate on Windows as expected - The Key was not embedded in the BIOS.