Download SamFW FRP tool 3.1 or latest version from here.
Open SamFW FRP tool and connect your phone to the computer with a USB.
Using SamFW FRP tool, go to MTP tab and click on "Enable Secret Code for Verizon". See the picture below. Note it works on any US CSC even though it says "for Verizon".
That part.
The codes do not work for me, I assume without going through these extra steps.