If you were to make a window, using your pencil, draw about 5-6 long rectangles on the construction paper.
Once you are done drawing the rectangles, cut them out and throw away the scraps.
Once cut out, be in a dark room, put a flashlight next to the Gobo paper to reflect it on the wall.
This is how mine looks like, I did not have a model or a friend with me but this is how its supposed to look like.
Example: This is how its supposed to look like with a model.