how do you actually play it?
You must enter the levels pressing 'e' on pc, or the 'X' or 'A' button of the controller, being over the red thumbtacks on the world map. Once in any level use the same button to interact with the items of the map and try clean it up somehow
i mean how do you actually play it once you have downloaded the file
On windows decompress the .zip with winrar or similar and double click on the .exe file
In Mac drag the app folder to the Mac app folder and execute