I had to do this post in 2 uploads - so sorry if it seems confusing. It's one continuous post.
This would be really cute on short hair too. You also could do it on both sides to make it look more like a headband.
To french twist hair: Part the hair on the regular part. Then slice down toward the ear, parting the
hair on it's side. It doesn't show in this picture but you want to brush all the hair forward so it stays in a tight french twist.
Take a chunk out of the part & split it in half. Start twisting the hair & after each twist, pick up a small piece of hair from the right side (or if you are twisting on the left side, pick up a small piece of hair from the left) & twist again, pick up another piece & keep on going until you get where you want to be. (Just like picking up pieces in a french braid but only from one side)