Stand your bike upright with your kickstand.
Use your socket or adjustable wrench to loosen the axle nuts on both sides of the rear wheel hub.
Set your bike down on its left side.
Stick the cone wrench into the right-side cone, located on the hub.
Turn the cone wrench clockwise until the cone just touches the bearings. Turn it back counterclockwise 45 degrees.
Tighten both axle nuts with your socket or adjustable wrench.
Stand your bike upright. Lift the rear wheel off the ground and move it left to right. Note any play.
Spin the back wheel to check there is free movement in the bearings of the rear hub.
Fine tune the adjustment, if needed. For wheel play, re-tighten the bearing cone. If there's resistance in the spin, loosen the bearing cone a hair.