Turn off the water to the shower by shutting the home water line at your water heater.
Remove the handle to the Delex faucet by taking out the set screw in the handle base with an Allen wrench and pulling the handle backward off the faucet.
Remove any adapters on your faucet by unscrewing their screws with the Allen wrench or screwdriver.
Remove the bonnet and retaining ring by unscrewing each one with your hands, or a pair of large pliers if necessary. If an O ring is under the retaining ring, remove it and replace it with a new one. This ring, if cracked, will cause leaks around the base of the faucet.
Remove the cartridge under these parts by sliding it out of the faucet's body and replace it with a new faucet cartridge from the repair kit. Replace the retaining ring and bonnet, adapters and handle to rebuild the faucet.