“Every now and then you may wish to display something from your iPhone or iPad on your Mac,” Topher Kessler writes for MacIssues.
“This may be during a presentation, or just for kicks, but if you have content on your phone and while you can always use various sharing services to send content to people or even to your Mac for displaying,” Kessler writes, “another very quick approach can be done if you simply have an available lightning cable.”
“Since this is a movie recording, you can click the record button to capture what your screen is showing, but if you want audio from your phone to also be recorded then be sure to choose your iOS device from the same drop-down menu next to the record button,” Kessler writes. “If you use your Mac’s microphone then you can narrate what you are doing to your recording, so this default setting may be preferred in some cases.”
Full instructions here.