Do have the Itch.io launcher? If you don't get it here https://itch.io/app.
Once you have that, you may have to reinstall the game from the launcher, but other than that. You should be set.
After you download it again, if you had to, go to the library tab within the launcher and there should be all the games you download.
If you get anymore games from itch.io, download them from the launcher. This makes the games download straight into the launcher.