Overlay in video - how to do?

Hi. I search method to make video overlay with using toastmasters meeting. Its issue is that it requires the installation of OBS and I have problem with complete installation this. I will try to correctly add this program again, but I don’t know if it will work (I trying install this on mac , maybe this is problem)

One result I found is (which might fit the solution to the problem): Capture a MediaStream From a Canvas, Video or Audio Element  |  Web

Virtual Background could be an option if I could figure out how to control it.