You can then import your guest(s) track to the GarageBand session that you created for your personal track.
I recommend recording your personal audio track using GarageBand while you are conducting your interview. I’ve found that the sound quality is a bit better this way. For this, all you have to do is open and run GarageBand while you are conducting your interview on Riverside. You can then import your guest(s) track to the GarageBand session that you created for your personal track. This sounds confusing, but I promise you, once you actually do it, it’s quite easy. Remember, prioritize sound quality above all else!!!