Make sure that the tablet is totally powered off. Press & hold both the UP and DOWN volume buttons at the same time.
Press and hold the power button until the tablet buttons light up. It will take a minute to happen, but when they do immediately let go of the power button ONLY. Keep holding down both the UP and DOWN volume buttons. You only have a second to do this before the tablet will continue boot up as normal. If that happens start with step 1 again.
After a few seconds of holding down both volume keys the screen will show the Vizio logo. Then the logo will change to a TRIANGLE with an exclamation mark.
Now let go of the volume buttons.
Tap the home button to pop up the boot recovery menu. Follow the instructions to reset your tablet. Pressing the up/down volume buttons allow you to scroll up and down the list. A quick press on the power button will accept your selection.