https://www.youtube.com/watch?v=rKpHb1PFQ1c

Remove the 6 screws
Safety check your gun
Punch out the 2 pins
Thin screw, thick screw
Screw them through the backing plate
Don't over tighten the screws
...and now the shell holder
Use the 6 little screws
Done

It takes only 10 mins to install it

Product Information:

The best way to carry extra rounds in the most convenient and accessible location for quick reloading without losing sight. Mounts directly to the shotgun receiver with an aircraft-grade aluminum mounting plate. All mounting screws and hex head wrenches included.

Technical Information:

This mount will not work with the factory forend on most magnum shotguns. To use the 6 round carrier, forends that cover part of the receiver during cycling will have to be replaced with one that does not, such as Advanced Technologies Tactical Standard Forend