Remove your drapery panel from its rod.
Steam or iron the fabric to release any creases, especially along the top of the panel.
Measure the width of the panel to ensure that it is at least double the width of the window. If you are hanging two panels on your window, each should be the same width as the window.
Lay out the curtain panel wrong side up, with the header completely flat and smooth. Measure the width with a measuring tape.
Cut off a length of drapery pleating tape equal to the measurement, plus 1 inch. Drapery pleating tape is 3 3/8-inch-wide cotton tape with pockets at regular intervals for four-prong pleating pins.
Pin the drapery tape to the top edge of the of the wrong side of the drapery panel. Pin a half inch of each end under. Ensure that the pocket side of the tape is up and the opening is at the bottom edge of the tape, toward the bottom hem of the drapery panel.
Thread a sewing machine and bobbin with all-purpose thread that matches the drapery panel. The sewing machine should be loaded with a universal needle.
Sew the drapery tape to the panel with a straight stitch along the top edge. Your stitching should be about a fourth inch down from the top edge of the fabric and above the pockets for the drapery pins. You don't want to sew the pockets closed. Remove the straight pins as you approach them. Turn at the end of the fabric, and stitch down the short end of the drapery tape. Turn again, and stitch back down the length of the drapery tape, a fourth inch from the bottom edge of the drapery tape, directly under the openings for the pockets. Some drapery tapes come with dotted lines to guide your stitching.
Insert the first leg of a drapery pin into the first pocket on the drapery tape. Insert the second leg of the drapery pin into the next pocket, pinching the fabric together. Repeat for each leg of the drapery pin. You should now have a pleat with three folds on the front of the drapery panel.
Skip three pockets, and repeat Step 9 with the next drapery pin. Continue in this pattern until all the pins are in place.