Record audio only:
Open Camtasia or select File > New Recording.
Click to disable the screen option.
Enable the desired audio (microphone or system audio).
Click the red button to start recording.
After recording, the audio clip appears in the Media Bin.
Record voice narration:
Open Camtasia or select File > New Recording.
Click to disable screen recording.
Microphone recording is enabled by default. Select the audio device from the dropdown.
Test the audio level by talking as you would during recording. You may need to lower the audio input volume if the audio input meter displays any red.
Mute the system audio and disable the system audio recording.
Click the red button to start recording or press Command-Shift-2.
Open the video clip to narrate.
Press Command-Option-2 to stop the recording or Command-Shift-2 to pause the recording.
After recording, the audio clip appears in the Media Bin.