Measure the height and width of the window with a measuring tape.
Measure the drop cloth and mark the cut lines with a pencil. The drop cloth should be about 3 inches longer than the height of the finished curtain and about two to three times the width of the window. Cut the drop cloth along the cut lines.
Fold 1 inch of the sides and bottom of the drop cloth over and sew along the seams with a threaded sewing machine. Tie and cut the end of the thread with scissors.
Fold the top edge of the drop cloth over about 2 inches and sew along the seam to create a loop for the curtain rod. Tie and cut the end of the thread with scissors.
Dye or paint the drop cloth as desired with fabric dye or paint to create a custom look for your curtain.