itch.io

If you bought it here, on itch.io, you can just go back to your download page and download the new version. You can find your download page here: https://itch.io/my-purchases

It'll be easier to add the game to Steam with the key on that page, where the game will update automatically

hah this might be a bit late but i finally did it, i deleted the old version and then downloaded the new one. ik there's like another way but i couldn't figure out the other way