Recording two inputs

All the videos are basic, in one sense. The problem is that this isn't a 'basic' thing to do, and because it involves a lot of complex routing outside of Audition, Audition isn't the best app to try to do it on. At its heart, Audition is editing software, not a communications package. On top of that, you haven't even said if this is for a Mac or a PC...

You might want to read this thread, and note especially the recommendations at the end of it. This is, I'm afraid, the only sensible approach to this.