They are pretty simple to install. Lift the playfield and hold the mirror blades up at each end with a couple of spring hand clamps. Position the blades as far back as they will go and just below the glass channel Along the side. Attach the back with one of the supplied screws, do the same for the front (you can predrill, but I usually don’t do that). If the washer at the flipper button interferes, loosen it and slide the mirror blade behind it. No need to do the middle screw. No need for any backing on the mirrors either.

I would remove the metal piece Held to the side of the cabinet with two screws in it, it’s not really needed.

The whole process should take 10 mins to do both of them,