Open the cabinet doors above the existing microwave, locate the power cord and unplug it.
Have someone hold the underside of the old microwave as you unfasten the four retaining bolts or screws with a screw gun.
Pull the old microwave away from the cabinet carefully and set it aside. Unpack the new above-the-range microwave.
Hold the new above-the-range microwave under the cabinets, pressing upward against the cabinet bottom. Insert and tighten the new retaining bolts or screws with a screw gun.
Plug the power cord into the electrical outlet. Set the date and time, following the instruction manual.