after you extract the download, there should be an application that says "sunnyDayJackGame"! if you have windows defender on, it might stop you from opening it the first time - just press "More info" and it'll give you the option to run it anyway.
in the game itself, the play button will appear after a few seconds on the title screen! you can also press enter or spacebar to make it appear. i hope that helped <3!