Go to your downloads on your computer and then find this games file in there. Double click the file, and then double click again on the file that says app next to it. Then a thing should pop up on your screen that says you need to extract the file so press the extract all button. After that you just gotta wait for it to download and then you can see the app in the file. Then just click it and it should open the app :)
Sorry if this is a bit confusing, I tried to explain it the best way I could <3