Turn the shower water off from the faucet. Leaving the water on will cause a mess and make the task difficult, so turn it off completely.
Remove the shower head by grabbing it tightly and twisting it off in a counterclockwise motion. If you cannot twist the shower head off with your hands, use a pipe wrench. Twist the adjustable knob, located at the top of the pipe wrench handle, to open the wrench enough to fit it over the connecting part of the shower head. Once the pipe wrench is in place, maneuver the adjustable knob until the wrench is firmly fitted around the base of the shower head and twist.
Remove all old plumber's tape from the pipe.
Dry the threads of the pipe thoroughly with a rag. This will allow the plumber's tape to cling to the pipe better.
Wrap the new plumber's tape around the threads tightly so there are no gaps in the tape.
Twist the shower head on clockwise over the plumber's tape. Tighten it as much as you can with your hands, then turn the shower on to try it out. If the shower head is still leaking, tighten it with a pipe wrench.