Yikes that's small! So here are the steps. Basically you need either a pillowcase, two pieces of fabric long and wide enough, or one long and wide piece of fabric that you can fold (this is the better as you would only have 2 sides to sew rather than 3).
After you have your fabric draw the shape you see on the top right diagram on it. Cut it out. If you fold your fabric you won't have to cut the top line. Then you sew a nice folded hem on the bottom edges. After that you just pin the sides and sew. Voila.
OK, but how do you actually wrap it? I can sort of make a bun behind my head but it's HUGE and my ends all stick out the top making me look like a brown aloe plant. I pulled an inchworm and a beetle out of my hair after working in the woods yesterday and today it was full of, geez, some sort of dusty brown stuff, and spiderwebs... I just want to stay as clean as possible and a bandana only covers the front eight inches or so.