Turn off the power to the water heater at the breaker. Open the cover on the side of the tank. Disconnect the two wires on the element. Note: Make sure the water is drained below the element being replaced. Use an element puller (Image 1) to remove the bad element. Insert a screwdriver into the element puller to get more leverage. Remove the element (Image 2).
Insert a new element and tighten. Fill the tank with water above the new element. If there aren't any leaks, reconnect the wires. Replace the cover.