Bless this post 🙂 It helped a ton! I just wanted to add a note.

If anyone wants to add commentary too from their mic into OBS, go to Settings –> Audio. I added it in Settings instead of from the main screen where you add sources. It looks like this in the Audio tab for me.

Mic/Auxiliary Audio Device: iShowU Audio Caputure
Mic/Auxiliary Audio Device 2: Built-in Microphone*

*This is just me not having a quality microphone yet, so I’m using what the computer has. Obviously this will be different for those who DO have a nice microphone.