Grab the shower head and turn it counterclockwise to remove it from the pipe. This will expose the threads.
Dry the end of the pipe with a towel, the threads should be dry before you apply the compound to the surface.
Rub pipe compound over the threads on the end of the pipe. Apply the compound heavily to cover the threads.
Slide the shower head over the compound and turn it clockwise to tighten it. Make sure the shower head is tight before turning on the water.
Turn the water on for the shower and test the connection. If there is still a leak, you can tighten the shower head further using a pipe wrench. Continue tightening until the leak disappears.
Grab the tub spout with a pipe wrench and turn it counterclockwise until it comes free from the wall. Many spouts thread directly into the water pipe and unscrew for easy replacement. If you feel resistance from the spout, look under it for a retaining screw that goes into the wall. You may need to remove the screw first with an Allen key and then twist the spout out.
Take the spout to your local home improvement or hardware store. It is crucial to purchase a compatible replacement. Having the spout with you will allow you to select a matching spout.
Slide the replacement spout onto the pipe threads and turn it clockwise until it is flush with the wall and facing downward. If the spout has a retaining screw, you need to secure that in place, as well.