Need the ability to add outside audio. For example, to put a track over a video instead of just the audio the video already comes with
Thanks for writing in. You can import audio-only clips/soundtracks from your local or cloud storage accounts.
Try these steps
Click on the blue plus button > Select Media > Navigate to your local storage (iTunes etc for desktop or Audio for iOS) or cloud storage (CC, Dropbox etc).
Is that what you're requesting? Or do you want to separate the audio that is part of the video clip?