The instructions show you where to remove material.
If the trigger will not reset after modification, pull slide to the rear and engage the slide lock. Set the muzzle on the bench, exposing the underside of the slide. At the top of the striker channel is the striker tab, at the bottom is the striker sleeve. Using a punch, push the edge of the sleeve downward. This will allow you to slide the cover plate off. Once the cover plate is off, you may carefully disengage the slide stop and ease the slide forward and off while depressing the take down lever. The striker will come out as the slide is removed due to the sear being engaged.