How do I turn off the screen overlay?

[AC Question]

I'm trying to give whatsapp permission to use the camera on my phone, but a box keeps appearing that says "screen overlay detected", which re-directs me to settings > apps. When I open that, I get shown a few apps and told I can "select apps to allow their buttons, pop-ups, or other elements to appear over other apps you are using". It doesn't seem to matter if the camera is selected or not, I still can't use it in whatsapp. How do I fix this?