Hey, bud. Looks like you included the .exe but not the rest of the build files. For Unity projects, you unfortunately have to just use the whole build folder (unless you create your own packager or something). The cleanest way to do that would be to make a folder on your desktop and set that as your path when you build the project. That folder will contain everything you need to upload, including the .exe to play the game.
I made my submission in Unity too. You can check out mine to see how the folder should look. While you're at it, I'd be interested to see what you'd rate it too!