For four chairs, it will take approximately one yard of fabric and 1-1/2 yards of fabric for six chairs. Be sure to leave at least an excess of three inches of fabric all the way around the chair seat.
To attach fabric, first find the center front width of the pad and back, and mark. Do the same on the back and make a center mark. Find the center of the fabric. Fold fabric along center line and cut small notch (Image 1) for both front and back. Starting from the back, fold the fabric over and line up the notch with the center mark. When fabric is straight, start attaching staples, leaving the corners alone. Repeat above step to attach the front and then the sides. Use your spare non-stapling hand to smooth and straighten the fabric as you're stapling. Don't stretch the fabric so tight that the lines (if you're using striped fabric) are distorted. Trim extra fabric away.
At the corners, fold fabric over and pull down and away and staple in place (Image 2). Rotate the seat pad and repeat the process for each corner. Staple on dust cover material to hide staples and ends of fabric.