itch.io

If you still need help, right click on the file you downloaded and press "Extract Here", then after a few seconds a folder should appear next to it. open that folder and you should see another folder called "Clangen". open that too, and then double-click on the file called "Clangen" and that should start the game!

Basically what you need to do is open Linux terminal and then put in 

/bin/bash -c "$(curl -fsSL https://install.clangen.io/stable/linux-glib2.31.sh)"

It should download the game for you after that and you can play and for a better guide you can use this docs sheet under the Linux area.

Here