Video tutorial
Specific steps
First connect both microphones to the computer via USB ports and make sure the two distinct microphones can be detected in the computer’s audio settings
Next launch OBS
In the Sources panel of OBS click Add Sources select Audio Input Capture then choose Create New pick the first microphone under Device and finally hit OK
Repeat the above steps namely click Add Sources in OBS Sources opt for Audio Input Capture select Create New choose the second microphone from the Device dropdown and click OK
By doing so two separate audio tracks for microphone recording get configured with AU-A04-1 and AU-A04-2 taken as example microphones here
Lastly tap Start Recording to begin capturing and export audio files containing dual-microphone tracks