How to put transparency background on video

[Julissajulietjiji0101]

I have tried so many solutions to put a transparency background on this video I tried outputting it with video encoder it shows black QuickTime it shows black I used alpha res 4444 still black i put the background to transparency it still comes up black I tried putting it in premiere pro it still is black . How do I get a transparent background on my video I'm on Character animator I have a Mac computer one of the new ones with Mac OS Big Sur update anyone please help how to get a transparency background.

[Jeff Bellune]

Have you tried putting your video in track 2 and an image (any one will do) on track 1 underneath it to see if it composites correctly?