Open up the door so you can access the lock on both the inside and the outside. Locate all of the screws holding the locking mechanism in place on both the interior and exterior of the door. Remove all the visible screws with a Phillips-head screwdriver and set them aside.
Pull off the cover on the inside of the door once the screws are removed and locate the set screw on the underside of the interior door handle. File down the small set screw until it is loose enough to pull off by hand.
Grab the handle on the inside of the door and pull it off by hand. Remove the four screws holding the interior door plate in place and remove the two screws on the interior of the door, holding the exterior handle in place with a Phillips-head screwdriver.
Push through the door from the inside and remove the cylinder. Remove the exterior door handle from the door. Loosen the screws and remove the cylinder on the side of the door. Clean off both sides of the door with a rag. Wipe down the entire area so it is spotless when you install the new locking lever.
Set the new locking lever in place on the exterior of the house. Drill two provided screws through the predrilled hole from the inside of the house to the outside just like the previous lock was installed. Set the interior lock in place exactly where the old one was removed from and tighten it down in place with the provided screws.
Set the cylinder in place and tighten it down exactly where the old one was removed from with a Phillips-head screwdriver. Screw the new strike plate over top of it. Open and close the door to test that it is working properly.