Locate house electrical panel and turn off power to the garbage disposal.
Locate water valve under the sink and shut off water to the kitchen faucet.
Disconnect discharge tube and connection to the dishwasher.
Insert screwdriver into existing mounting ring to the right of mounting lugs and twist counterclockwise wise to dismount existing garbage disposal.
Unscrew the electrical plate at bottom of the disposer and disconnect electrical wires.
Remove snap ring and pull out the mounting assembly.
Use screwdriver to loosen the nut holding the flange and remove the sink's flange from the top of the sink.
Clean old putty from the sink.
Apply a rope of plumber's putty to the new flange and press into place. Place a towel in the sink and use the old garbage disposal as a weight to prevent the flange from moving.
Get back under the sink and insert gasket, second flange, mounting and snap ring in this order.
Use the screwdriver to tighten the screws towards the flange.
Insert hammer into cover plug and tap with the hammer to open the dishwasher connection.
Locate and remove the cover plate to the electrical connections at the bottom of the new disposer.
Connect wires according to their colors. Typically white to white and black to black. Wrap electrical tape around wires.
Connect grounding wire to green screw.
Push wires back into disposer and replace electrical cover.
Connect discharge tube and clamp to disposer.
Lift disposer towards mounting assembly and insert mounting gasket. Align the three mounting tabs with ridges and lock in place by turning lower gasket with a screwdriver or wrench.
Attach discharge tube to disposer and wall connection.
Attach dishwasher tube to the air gap.
Turn electricity back on. Run water into the sink and turn on the disposer. Test for leaks on connections made.