Turn off the power at the circuit breaker or fuse box. There are a few easy ways to confirm whether you correctly turned off the power: try to ring the doorbell, or if the doorbell had been illuminated, check to see if the light is still on. If the doorbell was broken to begin with, rely on a voltage detector to test the wires.
Depending on the shape of your doorbell, the screws for new doorbell may not land in the same location as your old screws. If the trim underlying the doorbell is wood, patch the screw holes with wood filler and repaint. If the underlying material is vinyl, take a bead of caulk and plug the existing screw holes to prevent moisture from seeping behind the trim.
The needle-nose pliers will be helpful when it comes to attaching the small wires to the small screws on the new doorbell. Once the wire is wrapped around each screw, tighten the screws on the side of the doorbell using the screwdriver, ensuring that each wire is firmly connected beneath the screws.
At this point, turn the power back on, and see that the wiring is correct by checking for a light on the product (if applicable) and pressing the button to make sure the doorbell rings. Some transformers that reduce the voltage for a doorbell operate regardless of which wire connects to each screw, but if you aren’t able to get it working, just turn the power back off, swap them, and try again. If your doorbell was broken to begin with and you’re still having issues, you may need to replace the transformer itself.