How do you raise free chlorine levels in a pool?

You need a test kit to determine free chlorine levels. To reach those levels you test the water and add chlorine until you achieve the required amount ( 1.5 to 5.0 ppm) of chlor. The first reading on the kit is available chlor. The second part of the test would determine the free chlor level. The free chlorine is what is doing the sanitizing or killing of bacteria. The first reading only tells you that you have some chlor in the water. It is probably not safe to use the pool if you do not have a sufficient amount of free chlor. k