Turn off power, turn off water supply to heater. Remove wires from element. If the heater is in an area where water will not cause damage, unscrew and remove the element. Hold a rag over the opening while doing it to minimize air entry and water draining out. Insert new element. Reconnect wires. Turn on water and drain out air through a faucet. Turn on power. If the heater is in a finished area, then you will have to drain the water out before removing the element.