Read the forums. Realized that after a decade I do in fact have a stardock.com account. Logged in. I have the serial. Do I not also need a download or something? As in, perhaps, some files installed on my PC into which I input the serial # ? Like, maybe a link to some kind of file?
You have to activate the key on Steam. If you don't have an account, you have to create one. Then, when in Steam, go to "Games" along the top menu bar and select "Activate a Product on Steam". From there your download should start right away.