Summarize the following:
Before you take your valance piece to the sewing machine, place a pin in each of the valance's corners to help keep the folds in place. You may place more pins if desired, but the creases you created with the iron should be enough to keep the fabric in place for sewing. Use your sewing machine to sew a straight stitch all along the edge of the inner fold on all 4 sides of the fabric. Sew about 0.25 inches (0.64 cm) from the fold all the way around to secure the folds. However, make sure to keep the stitching on the inside of the fabric. Do not sew all the way to the outer edges. Remove the pins as you sew. To ensure that your curtains have a strong seam to hold them on the curtain rod, sew an extra straight stitch along the bottom edge of the top fold. Sew about 0.25 inches (0.64 cm) from the bottom of the fold and sew all the way across the bottom of the fold so that the outer edges of the valance will be secured as well. To complete your valance, remove it from the sewing machine and trim away any excess threads. Slide the valance onto your curtain rod by inserting the rod through the loop you created. Then, hang the curtain rod and fan out the valance. Make sure that the print side of the valance is facing you when you hang it.

Summary:
Place a pin in each of the corners. Sew a straight stitch 0.25 inches (0.64 cm) from the inner edge on all 4 sides. Sew an extra stitch along the bottom of the top fold. Trim away any excess threads. Hang the valance.