Measure the distance from the top of each bedpost to the top of the next, length-wise and width-wise. Write down these measurements. Add an extra inch of width and height for the hem allowance. Determine whether you will be adding additional fabric fringe to hang down around the posts. Add these figures to the original measurements to determine the total size of the fabric to be hung from the bedposts.
Cut out the fabric to the dimensions noted in Step 1. Fold over 1/2-inch of the fabric edge, all the way around, and pin it in place if necessary. Iron the edge to make it straight.
Sew a hem along the folded edge with a standard straight stitch. Use thread that matches or accents the fabric. Sew two lines of hem stitching for a larger hem.
Position the fabric in place over the bedposts. Allow it to droop as much as desired over the edges and in the center or stretch it tight in the center, depending on your preference.
Staple the fabric in unobtrusive locations at the very top of each post. Use multiple staples in each post to evenly distribute the weight of the fabric among the many small holes and prevent the fabric from tearing out one large hole.