How do I cover a wall to make a movie room?

Blackout curtains or drapes! Best of both world's.

Use a roll up shade that is black out. Cover with barn door style curtains. Or make theater style velvet drapery with black out lining.

I'd use light blocking (also called room darkening) mini blinds and curtains in a dark color. With that, you can always open the curtains and blinds and let the light in. Both my kids have the light blocking blinds and the light blocking curtains in their rooms since they are teenagers and want to sleep into the afternoon. My son has black curtains and my daughter has dark purple.

Hi! How about sliding barn doors? If you left the finish smooth, you could use them as a screen.

https://www.remodelaholic.com/simple-diy-barn-door-tutorial/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed:+Remodelaholic+(Remodelaholic)&m

curtains for the basement walls/theater | For the Home in 2018 ...

https://www.pinterest.com/pin/258816309808005364

How do you want the windows to look from the outside? Start with the material you want to be seen from outside (sheers, blinds, shade) hang that material inside the frame. If these windows have molding, create panels like artist canvas that are large enough to cover the molding. You can stretch canvas over the frames and paint it a dark color or design or you can stretch dark fabric over the frames. Hang the panels over the window frames. Your panels should be light enough to attach with Command hook and loop.