You can add drapery panels or up down cellular shades but make sure you select a light area rug to hold on to as much light in the room as possible.

I have to disagree with curtains. There's hardly any wall space on the right side and none if you count the fireplace ledge. They would have to hang over and even into the fireplace. Wouldn't look nice and if you use it, also dangerous.

I think blinds or shades would be your best options.