Note that the points of the triangle have been labeled A, B, C in the photo. Place the triangle on a flat surface with point B facing you.
Curl point A up and under, bringing it toward you until points A and B meet. The curled edge from point A should lie on top of the edge between C and B as shown.
Hold points A and B together with your left hand, picking up point C with your right. Wrap point C around to meet points A and B in back. All 3 points align to form 1 sharp point, which forms the bag's cone.
Hold the bag with both hands, thumbs inside, and slide points A and C in opposite directions to make the upside down "W" as shown.
Fold the points of the bag down into the bag. Tear 2 notches along folded edge and fold notch down. Tape the outside seam of the bag if desired.
To use a decorating tip without a coupler, cut 3/4 in. off the end of the bag, then drop the tip in, narrow end first. Don't be concerned if the tip doesn't fit snugly. The icing will hold it in place.
To use a tip coupler, drop the coupler base, narrow end first, into the bag and push it down as far as you can. Holding the coupler and bag together in place with one hand, twist on the ring. When secure, tear away the tip of the parchment bag.
Unscrew ring, position the decorating tip on the coupler and replace the ring, locking the tip into place.