Turn the power to the disposal off at the breaker box. Disconnect the electrical wires from the disposal by twisting off the wire nuts. Remove the electrical wire from the circuit by disconnecting it.
Insert a Phillips head screwdriver into the retaining ring at the top of the disposal unit. Turn the retaining ring counterclockwise to release the disposal unit. Do this carefully as the disposal is heavier than it looks. Set the disposal unit aside.
Remove the disposal drain ring from the sink by turning the locking ring counterclockwise by hand. Remove the gasket and push the disposal ring up and out of the sink. Install a sink strainer into the bowl. Place the rubber gasket and retaining ring on the strainer basket under the sink to lock it in place.
Connect the drain tailpiece to the strainer under the sink by twisting it on clockwise. Install a T-fitting at the end of the tailpiece if the sink is a two-bowl sink. Connect the second bowl to the T-fitting and tighten the ring by hand to lock it in place. Connect the S-trap to the T-fitting and tighten the locking ring by hand.
Connect the other end of the S-trap to the drainpipe. Turn the locking ring to secure it in place. Turn the breaker back on for the kitchen circuit after you are sure you have removed the electrical wire for the disposal unit.