The game is released in "Seasons." Depending on which one you want, the platforms differ:
Obtain the installer or ZIP file from your preferred platform above.
If you downloaded from itch.io , right-click the file and select "Extract All" to a folder on your PC.
Approximately 4 GB of available space for Season 1. Finding the Official Game Guide
Launch the TFTUV.exe (Windows) or the equivalent executable for your OS.
