First, I took in the sides a bit so it wouldn't be so frumpy.
Fold each strip in half and sew raw edges together.
Turn right side out.
Get the seam to the center of the tube, and sew a gathering stitch (largest stitch possible) right down the center.
Pull one thread to gather.
Pin ruffle around each sleave. I like to pin and sew on the inside of the sleave, so I can see that nothing is catching under the material.
Sew all the way around the sleave, turning under raw edge of ruffle when you get to the end.
Lay out remaining ruffles on one shoulder, and pin into place.
Sew everything down, and it's done!