There’s a single white wire in my wall. What do I do with that?
Some switch boxes have a single, un-capped, neutral wire. To install the switch, strip the end of the wire so there is ¼” of copper showing. If it is long enough to reach the switch you can use it. If it is not long enough, connect it with one end of the white extension wire (included with your switch). Attach the other end of the extension wire to the switch.