Easiest method is by USB make sure its formatted to fat32.
1. Download the USB version of any image.
2. Unrar and send the vuplus folder to your USB stick. Or in some cases you may need to make a folder named vuplus then inside that folder create another named duo. The send the boot, kernel and root file to the duo folder.
3. Turn off the power at the back of the VU rear of the VU+ you'll find the switch near the power cable. Insert your USB stick in the front USB port.
4. Turn back on the power.
On the front display you'll see reading USB device, this takes a while then you'll see erasing then programming.
It will then tell you to remove USB and reboot. Reboot with the power switch at the back