Measure the length and width of your window. Write it down. Add 6 inches to the length and 2 inches to the width. Cut a piece of rich, textured fabric such as velvet or damask.
Place the fabric face down on a flat surface. Fold the bottom of the fabric upward, creating a 4 inch hem. Pin it in place. Fold the right, left and top sides inward 1 inch. Pin them in place.
Sew the hems securely in place with a sewing machine, removing pins as you go. Cut a length of trim, such as tassels or dangling balls, to the length of the the total of the right, left and bottom sides. Sew the trim to the perimeter of the curtain.
Attach clips to the top edge of the curtain, spacing them every 6 inches. Thread the curtain rod through the curtain rod clips and attach the rod to the brackets above the window.
Drill in a metal pull-back onto the frame of the window, one-third of the way up from the window sill. Pull the curtain back and behind this pull-back to create the basic asymmetrical shape.