As well as importing an existing audio file, you can record audio live using the Record button
Audio Notetaker will now record into the Opus format, see Opus Encoding for more information.
You should use the standard Mac controls to select your audio source and set the recording level. You can do this by selecting Sound in System Preferences:
Set the input volume such that during normal recording the input level display reaches at the very least half-way. If at the maximum volume the input level is still too low, try to get nearer to the speaker. Audio Notetaker has a recording level indicator in the bottom left corner so you can continue to monitor the recording level once you’ve started recording, though note that this uses a different scale to the one in Sound.
Some digital recorders (e.g. the Olympus DM-450) have a menu setting that allows you to use them as a microphone when connected to your Mac. You will need to find the "USB" menu setting, select "USB Composite Device", connect the recorder to your Mac and then select it when it appears in the above dialog box (as "Microphone Streaming (DVR)"). Then your Mac will use it whenever it is connected.
You can control the amount of disk space used per hour of audio in App Menu → System → Settings → Audio Files