Greetings. I am trying to avoid the middleman and record an archived podcast directly into Audacity on my mac. However, I can’t figure out which input to select. I normally record into my DAW (LUNA), then move it into Audacity for editing. I am using an Apollo twin and and an Apollo 8p. Everything is connected via Thunderbolt, which I selected in Audacity. Any advice greatly appreciated. Thank you. I have Audacity 2.4.2.
Hopefully, by now you’ve found a solution to your issue. 
If not, (I’m not a MAC guy) (nor Apollo), here is an discussion that might steer you to a solution:
http://www.vo-bb.com/phpBB2/viewtopic.php?p=242951
I hope this helps.