To update your bluetooth/microphone/speaker settings, click on the camera icon to open the recording window

Tap on the gear icon next to the record button

Mobile

Desktop

 

Select the appropriate camera (including virtual cameras) and microphone that you'd like to use 

Desktop

Mobile (iPhone)

If a webcam or microphone isn't showing up that you expect to see there, try restarting the computer or phone, unplugging and plugging back in the camera/microphone, and checking again.