Remove the Cylinder Plug
Unlock the door knob with the key, and pull the key out of the door knob. Remove the screws on the inside door handle with a Phillips-head screwdriver. Pull the inside door handle and the outside door handle away from the door.
Find the tab between the half round stem on the outside door handle and the back of the door handle plate. The half round surrounds one side of the spindle. Push the tab with a flat-head screwdriver so that the tab is in line in between the two sides of the half round stem. Insert the point end of the cylinder removal tool into the center of the spindle. The cylinder removal tool is the long round tool in the rekeying kit. The tool has a point on one end and a fork on the other end. Turn the spindle so the the tab at the bottom lines up with the mounting sleeves on the door handle.
Slide a flat-head screwdriver under the retainer clip at the base of the spindle. Pick up the door knob and point the spindle toward the floor or work bench. Pry the retainer clip slightly with the screwdriver until the spindle releases from the door knob. Turn the knob so that the inside is facing you. Locate the upper hole inside the center of the retainer clip by the half round. Angle the fork end of the cylinder removal tool between the half round and the retainer clip with one point of the fork in the hole.
Hold the outside of the door knob with one hand over the key cylinder. Push down with the cylinder removal tool to disengage the spring clip securing the key cylinder. The cylinder will fall into your hand.
Place the fork end of the cylinder removal tool between the back of the cylinder plug and plug retainer. the plug is the actual part of the cylinder you rekey. Push the plug retainer away from the plug with the cylinder removal tool. Insert the existing key into the cylinder, and turn the key 45-degrees either left or right. Insert the plug follower on the back end of the cylinder plug. The plug follower is a short tube that is the same diameter as the cylinder hole in your lock. Push the follower through the hole, pushing the plug out of the cylinder. Continue pushing until the plug is out of the cylinder and the follower is protruding on both sides of the cylinder.
Rekey the Cylinder Plug
Turn the plug over to dump out the existing tumblers. Take the old key out of the plug and insert the new key from the kit. Place the new tumblers into the plug in the order the kit instructs. Each kit has a specific numbering order for the tumblers to engage the new key correctly. All the tumblers should be flush with the plug.
Place the back end of the plug at the front end of the follower. Slowly push the plug into the cylinder, pushing the follower back through the cylinder. Continue pushing until the follower is out of the cylinder and the front of the plug is flush with the outside of the cylinder. Slide the plug retainer back over the end of the cylinder plug with the cylinder removal tool.
Insert the cylinder into door knob until the spring retainer engages. Remove the key from the lock, and insert the tab end of the spindle over the top of the half round. Push the spindle into the retainer until it snaps into place. Twist the spindle clockwise with the cylinder removal tool to fully seat the spindle.
Insert the outside door handle into the door with the spindle going through the center of the latch assembly. Insert the inside door handle through the door and secure both handles with the two retaining screws.