If you are looking to stream or record video using OBS, please follow this guide to set that up for Mac or Windows.
Once you have installed the latest version of OBS and launched the application you will first see the main OBS page which will look like the screenshot below;
Now you are here, you will need to assign your audio inputs to OBS.
First click "settings" in the controls panel on the right hand side of the screen;
Once the settings page is open, choose audio on the left hand side of the screen to open the Audio Settings page.
The desktop audio settings refer too the output you want your desktop audio to be outputted too, as standard you can set this too Analogue Output 1+2, or any other output depending on your needs.
The Mic/Auxiliary audio will be your mic inputs into OBS, so for a mic connected to either input 1 or 2, it will be "Analogue Input 1+2" for a mic in 3 or 4, it will be "Analogue Input 3 + 4" and so on.
Please be aware that due to issues with the Mac version of OBS, it will only see the mic 1 and 2 inputs from your interface.
To get mono audio inputs from your microphones you will need to follow the guide here (Windows only); https://audient.zendesk.com/knowledge/articles/12915075189524/en-us?brand_id=2283536
You can check that your microphones are assigned correctly by checking the meters in the "Audio Mixer" panel.
Further settings can be accessed by pressing the "Cog" icon in the bottom left of this panel, which will take you to the "Advanced Audio Properties" Here you can access features such as panning and audio monitoring.
Now you will need to add your microphones as sources for OBS. Close the settings window, and then press the "+" button in the "sources" panel. Select "Audio Input Capture" and choose "Use existing source" on the next pop up window.
Which particular mic/aux you use, will depend on how they are configured.
You can then add any other sources, for example display video capture, or an external camera.
If you are using an interface with loop-back enabled, you can set this as your one of your OBS inputs to stream your desktop audio as well as combinations of microphone inputs. This is in place of the desktop recording functions built into OBS. (Please be aware that on a Mac, OBS cannot see the loop-back inputs).
You can find more information on using loop-back for your specific device here; https://support.audient.com/hc/en-us