Turn off both the hot and the cold water shut-off valves underneath the faucet before you start rebuilding your Eljer faucet.
If you have a double-handle faucet, you will need to use a screwdriver to remove the screw on top of the faucet. The screw will be located under the handle's hot and cold water decorative caps, which can be pried off with a screwdriver. If you have a single-handle faucet, use an Allen wrench to remove the screw on the bottom side of the handle closest to the base.
Remove the screw holding the stem in place.
Remove the old stem from the faucet. This will be the long brass piece sticking out of the body of the faucet under the handle, and pliers may be needed to remove the stem. Stems are threaded into the body of your faucet, so you will have to turn it counterclockwise to remove it.
Thread your new stem into the body of your Eljer faucet.
Place the handle or handles back on the new stem, securing them in place with the screw you removed earlier.