Put the disc into your Wii U console. Wait 5 seconds and you should now see the game disc icon appear on the Wii U menu. (it will change to a picture of that game/application) Use the GamePad ...

You can throwback up the image on the Wii U GamePad, by pressing the display switch icon once more to drop the image window down. The image will remain on the TV screen and the Wii U GamePad again.