When you download it, it should show you some instructions:
FOR MAC OS downloaders: I packed it as a .RAR file! You will have to use an unzip tool similar to WinRAR or WinZip to unpack it. https://apps.apple.com/us/app/the-unarchiver/id425424353?mt=12 This one should be an official tool but we haven't tried it!
If you still get an error (this application cannot be opened), try googling around, we found this: https://stackoverflow.com/questions/50577473/unity-game-compiled-in-windows-does...
I don't have a MAC so it's hard for me to troubleshoot.