Download and extract the image to a USB stick
Plug the USB Stick in the receiver.
Turn power off with rocker switch at the back. Give 3o secs turn rocker switch back on.
You should now get flashing lights, press the front power button, let it do its thing.
It will reboot, remove the USB or it will try to reflash again.
You should now be done, from here you can install your settings from backup or start from scratch