We connect a microphone to a device that converts a verbal response to a key press; when PsychoPy receives that key press we can use it to capture RT. If you don’t have such a device and want to get RT from a verbal response, you would have to use voice key functionality internal to PsychoPy. e.g.:
I haven’t done this yet so I don’t have much to say about how well it works. It seems pretty straightforward.