Dex works with the XReal Air and my Samsung Note 20, but I don't understand Nebula

When I first installed Nebula it was quite confusing. I seemed to lock up while updating the firmware even thought the completion bar went to 100%. that happened two or three times until it seemed to finally be updated.

Now that Nebula is installed it’s not making itself useful except providing the icon which turns the phone into a touchpad. When the glasses are in Dex mode and I start the Nebula app and select either the “AR Space” or the “Air Casting” button Nebula turns the glasses off. That’s fine I guess, but I can’t find any way to cast a video to the glasses after that happens.

Can someone please explain to me how and what Nebula is supposed to do for me in the two modes and what I do the make it happen?

Thanks