Masking using Circle effect leaves background black but I need it transparent to show other video

I placed a screen recording in my timeline and placed a video of me talking over the screen recording explaining what I was doing (for a tutorial). I wanted to get a perfect circle crop of my face talking so I used Effects > Video Effects > Obsolete > Circle. I then adjusted the radius and the positioning so that it created a perfect circle. The issue now is that everywhere that isn't that circle is pitch black. I need that part to be transparent so the video underneath shows. How do I do this?