Hi, simply follow the steps ingame:
- Click Login button
-> It will take you to itch.io via a browser
- Login to Itch.io using your Itch.io account (it will skip if you logged in already)
- Click Authorize
- Itch.io will give you a code and tell you to paste that code to the game. Do it as they said.
- Back to the game, paste the code Itch.io gave you.
- Enter