To install a new water pressure tank, remove the plastic inserts around the ports, position the tank, apply plumber's tape and install the nuts and washers. At this point, turn on the power to the tank and fill it until the pump shuts off. The tank is then ready for use.
Remove the old tank, and then remove the inserts that are on both the outlet and inlet port. Pry them out with a screwdriver, and then wrap three layers of plumber's tape onto the threads of the stub-outs. Screw each into the outlet and inlet ports on the tank, and make sure they are tight.
Put the tank in place, making sure the stub-outs point towards the connection unions. Secure the tank with anchor bolts, and then wrap plumber's tape around the threads of the connection unions. Align the ends of the unions, and then tightly screw the ring nuts onto each. Install the nuts and lock washers onto the anchor bolts, and use a socket and ratchet to tighten them.
Now that all of the connections are in place, move the relief valve handle to the open position, and then turn on the electrical circuit through the breaker. If there is air in the system, allow it to escape through the relief valve, and then close the level of the valve as soon as water begins to stream out. Allow the tank to fill with water until the pump turns off, completing the installation.