I've made a curtain for inside before.
I made a rectangle of fabric, slightly larger than the window and hemmed the sides. Along the top and bottom of the curtain I sewed a casing. I also sewed a couple of tapes to the bottom edge of the curtain.
I used a curtain wire, threaded through the bottom casing, the fixed into screw eyes at the bottom edge of the window.
At the top of the window I screwed a couple of cup hooks into the wall. By threading a dowel through the casing at the top of the curtain and resting it in the cup hooks the curtain stayed in place covering the window. When I wanted it out of the way I rolled it up and tied it with the tapes attached to the bottom edge.
It's kind of hard to explain but was pretty easy to make and worked well.
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