Without built-in loopback on your audio interface you’re not able to record your mac desktop audio without a paid app like Audio Hijack.

This video explains how to record desktop audio from an Apple computer within the OBS Studio software.

Software Download (Mojave and earlier)

Software Download (Mojave/Catalina)

audio hijack single

Record any application’s audio. Save audio from hardware devices like microphones and mixers as well. Mac only.