When you download (using the top download), you'll get a .zip file which you should unzip with 7zip or whatever else your computer might have. This will make a folder in which there is a file called "main". Just open that and the game should pop up!
Are you sure you downloaded the main file, not the "source" one? If you did and it's still not working, then can you tell me exactly what steps you're taking and how it isn't working? (if you have discord, it may be easier to discuss this there. you can dm me at sky#3890)
