Setup based on the Oculus Support Guidelines nott working, incomplete or outdated

Hi All,

I am writing you since the Oculus Support can't help out and asked me to get in touch with you.
this is the link I used when I tried to setup mixed reality capture.
I'm very techy so I think I just missed setting.

When I try to setup OBS Live/Studio (I downloaded the version and the plugin the MRC App requested), I can't go pass setting up foreground and background.
Once I selected the black/white from i.e. beatsaber windows (to use a background) and set everything up as discribed in the video. It asks me to select the same window to setup the background. This is technically not possible apparently. Even after selecting it doesnt show me anything. The video for the OBS setup is partially missing or hidded while its being explained.

Can yo uprovide more clear guidelines or update the existing one?

Thanks,
Leon