Hi Alyssa!
It sounds like you were looking for a way to add audio, globally across a Rise 360 course!
I'm happy to share that we are tracking a feature request to give authors that ability! I've linked this discussion to the feature report and will provide updates if it makes it onto our Feature Roadmap.
In the meantime, as a workaround for Rise 360, we suggest editing the published output to include the desired background audio. However, this would not be applicable in Rise.com.
Please let me know if you have any more questions!