Turn off the home's water supply.
Take off the Delta shower faucet handle by removing the set screw, which is located either on top of the handle under the cap (pry this off first) or in the side of the handle near the base. Then just pull and the handle should come off.
Take off the bonnet and trim sleeve. Loosen the bonnet by turning it to the left. Pull out the stem assembly, also called the cartridge, by lifting it out of the head of the faucet.
Take out the seats and springs located in the back side of the cartridge by prying them out of the holes with the tip of a screwdriver.
Apply silicone grease (plumber's grease) to the new seat springs and insert them into the cartridge, washer side first. Push them into place with your finger tip.
Re-insert the cartridge and replace the bonnet, trim sleeve and handle.