Launch the TFTUV.exe (Windows) or the equivalent executable for your OS.
If you downloaded from itch.io , right-click the file and select "Extract All" to a folder on your PC.
If you own the Steam or GOG versions, the is usually located in the game's installation directory. You can also access it ingame by pressing the "Bonus" button on the main menu. Tales From The Unending Void: Season 1 on Steam