The REAL answer is that you have to go into your Melodyne folder, click Setup.exe (i'm on windows), go through the setup.
Then OPEN the Melodyne standalone app. It will ask you if you want to activate. You do.
Click ACTIVATE. It will take you to melodyne website and force you to open an account there, just to activate the product.
*** If you close the browser during activation because you actually have no interest in having a Melodyne account, your activation will not go through. Also, then when you click to try to activate it again, the melodyne website will no longer give you the option of simply activating. it will instead ask if you want to BUY a license. You don't. I had to close the browser and melodyne app for it to give me a new activation pathway which worked after registering for the completely useless account.
To actually use Melodyne in Studio One, right click on an event, scroll to the AUDIO submenu, and click EDIT WITH MELODYNE (or shortcut CTRL M).
What a frustrating way to make us activate something that was "included" in my purchase.