Ok, it sounds like you’re trying to run the rar. A rar is a file like .zip, it’s a compressed file that you have to use a special program to decompress it first. 7-Zip is what I use, it’s free and very well known.

Download and install 7zip from here: if you have a 64 bit machine, then select the windows 64-bit x64 option. If you have a 32-bit machine, then select the 32-bit x86 option. There are other free ones that you can use, such as winrar or winzip, but I recommend 7zip.

Once you’ve installed 7-zip, restart your computer and try again. If it doesn’t work automatically after that, we’ll dig a bit deeper. One more question, are you opening it through the itch.io app, or are you downloading it from the itch website?

Also: The devs release a new version of the game monthly. A new version will be out in (likely) a day or two with new content, so you may want to wait just a tiny bit.

I've run into that with both WinRar and 7zip. It usually only happens with LARGE archives. Instead of double clicking on the archive, right click on it and select one of the extract options.