Put your blouse in "wrong side" position
cut your sleeves.(You don't really need the ruler is just to explain you where to cut)
after curt both sleeves from the blouse, cut out the neckpiece
make a straight cut on the edges of each sleeves
cut elastics with the same centimeters that around the border of the sleeves
go around the edges, pinning the elastics
If you prefer, You can sewing the edges and elastics together in a "overlock" sewing machine before go to a conventional home sewing machine.but I don't think it's totally necessary, ok?
fold one time, that makes the elastic goes to inside of the wool, and sew!I'm sewing like one centimeter away from the edges.You can use the distance you prefer.
tchadaaam!! thats how it looks like after the sewing machine!Have a good class of ballet .. or just have some fun at your streets.
You can also make in other sizes, cut more down the sleeves at the step 4!! Use your imagination, This is just the beginning.Create your personal leggings.