Line up the rear camera bezel with the cutouts on the rear glass, then set it down on the adhesive. Make sure the side with the camera lens cover protruding is facing the rear glass.

Make sure the camera lens cover is completely seated in the rear glass's camera cutout so that the bezel lays flat against the glass.

Use your fingers to apply even pressure to the bezel for 30 seconds to make sure the adhesive bonds properly.

Right before you install the rear glass and seal the phone, peel off the black backing covering the camera glass.