You need a pretty big shirt (Male shirts works best)
Sorry for blurry picture. But you lay it over your shoulders. Don't put your arms in.
Then find a shirt button that fits good on you. (for me it was the fourth from the top) then you fasten the buttons all the way down (Im sorry for really bad English)
Take a sleeve and ...
Do it on both of your sleeves and tie Them together.
If you want you can tie Them into a bow after you tie them together, But The longer sleeves you have, the more beautiful Bow you get :)
Done!! Really cute and it almost looks like some cowgirl style :)