Measure the height of your shower stall from ceiling to floor. Also, measure the length and width of the shower curtain.
Compare the height of the shower stall to the length of the curtain. Cut a piece of fabric to the cover the distance. For example, if your shower curtain measures 72 inches by 72 inches and your shower stall is 84 inches tall, cut rectangle of fabric measuring 73 inches wide by 12 inches long.
Fold the bottom of the pinned fabric up by 2 inches to create seam at the bottom. Fold toward the back side. Fold the right side in by one-half inch. Repeat on the left side. Pin all of the seams in place.
Thread the sewing machine with thread that coordinates with the colors in the original shower curtain and the fabric. Sew along all the pinned edges, carefully removing the pins as you sew.
Install the shower curtain rod as close to the ceiling as possible. Center the rod between the two walls of the shower and twist to increase the tension. Stop when the rod sits snugly between the two walls.
Hold the shower curtain liner and the shower curtain together. Match up the ends of the curtain and the liner with the slots for shower curtain rings. Slip rings through the openings. Hook rings around the curtain rod and snap them close. Be sure the shower curtain fabric is facing out.