itch.io

not sure if theres a way. but here's what i did: u download the game again and when it asks you to choose a file location, choose the location where the already downloaded version is in. the files have the same name so it will ask you if you want to replace the file. then click yes.

Go to the top of the page and you'll see a banner that says "You own this game" - click the nearby Download button. If you're using windows, download "That's Not My Neighbour.exe" (not version 1.0.3.3!), and drag it into the folder where your previous version is - windows will ask if you'd like to replace it, say yes. 

I have another comment if you scroll down, it includes pictures which may help.