I have a king size quilt that we use as a curtain on the doorwall from our bedroom to our deck. I don't imagine the window in your door is very large. I would make the quilted curtain more than 1 width of the window...1.5 to 2 times wider would be better. If you can, I would recommend that you use plain white backing if the back of the quilt will face outside as any other color will fade where the sun hits it...it also looks better from outside. Check at a home supply store or hardware for a curtain rod and curtain rings with spring clamps on them. If those are not available, you could always sew white plastic rings onto the quilt/curtain for hanging. Good luck with your project. Be sure to post photos when you are finished.
Wendy