How to make all screen black?

[ExpectedIdentifier]

Hello guys, I am working on a new project. I want to be all screen black. You can't see anything. And I'm going to show messages on screen. I will tell the story like that. I know how to show messages but I don't know how to make all screen black. So my messages look better with all screen black.

FadeOut(0); //This will fade the screen out instantly.

FadeIn(5); //This will fade the screen back in over 5 seconds.