How do you change camera in imovie to external camera

It is easier to record on your camera, save the video on your camera,  and then import the video from the camera into

iMovie.   You can record directly into iMovie with the internal Face Time camera but not with an external camera.  However, you can use the QuickTimePlayer app on your Mac to record directly with an external camera.

Here’s a link that explains how to record a movie directly with QuickTimePlayer. 

https://support.apple.com/en-us/HT201066

Unless you want to use the internal microphone, you first need to adjust the sound settings so that the Mac recognizes the

Logitech as an input device.  To do that, plug in the Logitech camera to your Mac and go to Applications/Utilities/Audio-Midi Set up and enable your Logitech as an input device in the sidebar. The Photos app might open, but if that happens just park it on the dock -- don't close it or it somehow reverts the setting you just made. Then close out of Audio-Midi Setup and open

System/Preferences/Sound/Input and confirm that your Logitech camera is now shown as an additional input device. Select the Logitech device by clicking on it. It turns blue. Make sure that there is no muting turned on via the other settings in the sound controls. Then close out of System Preferences and open QuickTimePlayer/File/New Movie recording. In the drop down controls next to the big red dot select your Logitech device as the audio input device. Adjust the sound slider to full volume. Then record a video with your Logitech, using the Logitech as your mic, and save the video to desktop. From there you can import

the video into iMovie.

-- Rich

Sounds like OS X doesn't see your camera at all.

Check >About This Mac>System Report>Hardware.

Do you see camera connected?

If no – check >System Preferences>Sound>Input.

Do you see your camera microphone as sound input source?

If no – you should make camera visible by OS X.

I think it's easier to record in QuickTime and import recorded video in iMovie.