When a starter is inserted into a video everything on that starter is automatically ported over, except for any sound files including music.
If the starter you'll be inserting in your video has audio attached to it (such as music, voice-overs or dialog) you can simply go into Your Library and find any sound clips you've recorded directly on the platform or even sound files you've uploaded that you recorded using a third-party tool like Audacity (Learn more here: https://support.goanimate.com/hc/en-us/articles/202558584?).
Simply click on each of the files you want to add to your video while on the corresponding scene and you'll be able to attach each clip accordingly. This makes is super easy to build videos!
You can find the sound files in your library here:
Step 1: Click on "Your Library" in the tab shown below
Step 2: Click the music tab and then "Voice-overs" to find all your recordings