The first step in shocking a pool is to check the levels of chlorine. That will help you know how much shock to use. You should also ask a pool professional which shock to use. When shocking a vinyl pool you should add the shock through the skimmer with the filter running. That will prevent burning or staining the liner. For more information on shocking a vinyl pool see
. http://www.wikihow.com/Shock-Your-Swimming-Pool.