How do I make an image transparent in Affinity Designer

[Monica Schultz]

Hi, I have a black png file and I would like to mask the flag and make the face transparent so it displays the flag. I can't seem to change or remove the colors on the black image, how do I go about that? 

[PixelPest]

Have you tried to set the Blend Mode to "Erase" or "Divide" for the flag already?

[DWright]

You can select the skull and use the Mask Below command in the layers to get this effect