The light bulb is in a sealed fixture that is secured with one screw usually and a hook on the other end. And what ever you do don't cut the extra cord when you pull it out. Suppose to roll it around the fixture as you put it back in, they leave it long so you can change it without draining the pool. Unscrew and get it out of the water. Remove cover and break seal. Wright down what fixture you have so you can get the wright seal and most pools use a 500 watt bulb so there's that. Reverse procedure and your golden.

Oh and try not to touch the new bulb to much and wipe it down with a dry clean rag. Seen the bulbs do wired things when you turn them on and they have oils on them. And don't turn the light on for to long with it out of the water.