Check that no power is being supplied to the doorbell wiring by holding a circuit tester against them. Feed the doorbell wiring protruding from the side of the house through the hole in the center of a doorbell mounting block. Push the mounting block against the siding and adjust it to close any gaps.
Drive 1 1/2-inch wood screws through each of the mounting block's screw holes. Loosen the new doorbell's screw terminals. Bend the two wires coming from the house into hooks. Hook one wire around each terminal. It does not matter which terminal each wire gets connected to. Tighten the doorbell's screw terminals.
Press the doorbell against the mounting block. Line up the doorbell's screw holes with the mounting blocks screw holes. Secure the doorbell to the mounting block with the provided screws.
Place a tube of silicone caulk into a caulk gun. Run a bead of the caulk around the seam where the mounting block meets the siding. Smooth the caulk bead with a finger.