[Need some help with Adding Text with opaque background]

I may have found my solution.  I added another layer and used the rectangle tools to put a black box there.  Then I added another layer and using the text tool, I put white text on the black.  This seemed to work out find

[Need some help with Adding Text with opaque background]

Hello. I am new to Affinity and I have something that I need to do, but Im a little stuck.  I have a video from Zoom where the presenters name is superimposed on the bottom left.  The trouble is that the presenter name is incorrect.  I wanted to use Affinity to create a text layer that I could add to iMovie to show the correct name.    Ive taken a screen shot from iMove and pasted it to Affinity.  Now, I am adding a layer and adding the text to overlay with the proper name.  The problem is that the name in the screen shot is still there.  So, I need two make the background of the text box opaque.  For example, white letters on a black background.  Maybe the solution is right in front of me, but I cant seem to get it.    

The goal is to take that text layer and save it so I can put it in with iMovie, Picture in Picture so that it is displayed on top of the incorrect name