Take it you are sorted bud?
The image is meant to "flash" you should see it changing from usb (a second or so) to flash and then leave it for 5-10 minutes. The box should then reboot and will be updated with the new image which you can then proceed to finalise set up.
If for any reason it aint happening I would be minded to d/load the image again just in case the first one was corrupted for any reason and just send to usb, put it in back of the box power off and on and let it do its thing.
Good luck.