Attach a 2mm narrow-hemming foot to your sewing machine, following the manufacturer's instructions for presser-foot replacement. For most machines, you will lift the lever on the rear of the presser foot to remove it, then insert the new hemming foot.
Fold over 1/8 inch of the tulle along 2 inches of the edge near the corner of the fabric. Fold over a second time, rolling the hem so the raw edge is caught inside the fold. Pin the fold in place.
Place the folded tulle under the sewing machine presser foot. Line the fold up inside the channel on the hemming foot.
Lower the hemming foot and stitch three to four stitches. Stop the machine with the needle in the down position. Lift the foot and remove the pin that was holding the fold in place.
Lower the foot and proceed to stitch the hem slowly. Guide the tulle through the machine using both hands. The foot automatically rolls and stitches down the hem.