Shut off the water and relieve the pressure, cut into the main cold line, run the supply into the tank's inlet and the outlet back to the house, put a bypass on it, then fill it slowly and flush it. I recommend having a plumber put it in: a non-backwashing carbon tank is an inlet and an outlet with no drain line and no electricity, about an hour or two of a plumber's time. Here is where the tank goes on city water and on a well, what ships, every step with a photo, the three-valve bypass loop, and installing it outside.