So I used a few pieces from the fabric my quilting mother gave me. It's a tensor rod at the top and a dowel at the bottom of the window. Just made a simple pocket for them. Was pretty quick to put together. The time was spent figuring out how far up from the floor to make the window. I drew it all out in chalk.
In the future, I would make the widow a bit narrower and perhaps make the curtains a bit longer. I put Velcro on the back so the kids can put the curtains up if they want during a show.