HUE Animation Studio defaults to using your system microphone. You can set the camera as your default system microphone at any time.
To do this, Quit out of HUE Animation and go to System Preferences, then the Sound pane, then the Input tab. Make sure that the camera is selected in the list and the input volume is set high enough. You should see the Input level gauge register sound if you tap on the camera’s head.
When all of this is set up correctly, close the Sound panel and reopen HUE Animation. It should register your microphone properly once it’s been set as the default in your Sound panel.