How to get the files?
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.