As long as it takes you to stick it to the wall.
It takes ~30 seconds to use the included 3M adhesive to mount the doorbell. Mounting the doorbell on a wooden door frame with the included screws should take a 1 minute.
Optionally, you can hardwire the doorbell using our Wyze Duo Cam Doorbell with our installation guide. You can install it as quickly as you can turn off the power at your breaker box, connect the wires, and turn power back on again.