First add your CAST as a video source in the bottom left panel by pressing on “+” and choose Video Capture Device from the dropdown.
In the window that now opens, confirm that you want to create the new input source.
Choose AtomX CAST from the Devices dropdown and leave the Resolution/FPS Type at Device Default.
Next, set the Color Space to 709 and the Color Range to Full.
To set the AtomX CAST as your audio source in OBS, you need to add it to your Sources by choosing Audio Input Capture from the dropdown.
Choose AtomX CAST from the Devices dropdown, and your embedded audio should now appear in the Audio Mixer panel on the bottom.
Make sure to hide the inactive Mono audio meter from the Audio Mixer panel.
Further adjustments such as dialing in the streaming bit rate and entering the stream key can now be made via the OBS Settings.