How to install an electronic door lock?
Installation instructions depend on the exact model of "electronic door lock" you purchase.

Most of the low-cost/self-contained units install into a standard cylindrical-lock bore (ie, in place of the normal knobset and/or deadbolt), occasionally with another hole or two to anchor them firmly in place. That's an easy retrofit.

Commercial-type units, where the electronics is separate from the door hardware, are more complicated.