I have a key for this from groupees, but I can't seem to get it to work. It just takes me to this page, where I can download the demos or buy the full game.
I answered on Steam, but will post this here, too:
Usually the key is a link. However, if it's just the key (a bunch of random letters) try adding this to the beginning: https://fascimania.itch.io/kilgazar/download/ If that doesn't work, contact me at firstname.lastname@example.org and I'll help you out. Please let me know either way.