Get an image

Make sure your image is newer than Sept 14, 2018 as that is when the overlay was added: https://github.com/beagleboard/bb.org-overlays/blob/master/src/arm/BBORG_GAMEPUP-00A2.dts

The image up on https://beagleboard.org/latest-images is currently: https://debian.beagleboard.org/images/bone-debian-9.5-iot-armhf-2018-10-07-4gb.img.xz

That should be new enough.

Install overlay

echo uboot_overlay_addr0=/lib/firmware/BBORG_GAMEPUP-00A2.dtbo | sudo tee -a /boot/uEnv.txt
sudo shutdown -r now

Sound

For now, a bit of a hack must be applied to get the sound to work:

https://github.com/jadonk/bb.org-overlays/commit/b6aecdd60acc25115531599223222f99d000b1b6