I would appreciate it if some one could tell me how to use the light isolating device that came with my package and what it is used for.

it's a great tool and can be used for many different situations. it's designed to keep water away from the light and thus a path to ground for your leak signal.
suck the water out from behind it and the pool water pressure will keep it in place.

I also use it to seal off main drains to fix underground leaks outside of the pool in the drain plumbing line. That way I don't have to dive to plug the drains.

Thanks guys for that information. I really had no clue. Sdewolfe and tcpools I appreciate this information.