-Paid(Premium) versions on Itch come pre-activated, you don't need to use your email in-game.
-If you haven't managed to download the paid version from Itch before it was delisted, read the below:
Paid versions on Itch are temporarily unavailable due to the recent complications with Payment Processors/Itch.
Paid versions should return in a few days assuming Itch resumes service for adult games.
If you can't wait until then, send me an email at cutepercentage@gmail.com with your purchase receipt attached, and I'll provide a direct link there.