Place triangle on a flat surface with pont A facing you.
Curl over point C to meet point A as shown.
Now hold points A and C together with one hand while you bring point B over and around to join the back of points A and C with your other hand. You have formed a cone.
Adjust points C and B to draw the top of the cone into a tight sharp point.
Tape the outside seam of the cone to hold it together.
Cut about 3/4" off the top of your cone to accommodate a decorating tube. Don't cut off too much, or the tube will drop right through. Trial and error will show you how much of an opening you need. The tube doesn't have to fit snugly, since the icing will hold it in place.
Put icing in your cone with a spatula, filling the cone no more than half full for ease in handling.
Fold the top of the cone as shown, with the sides folding in first and the top rolling down to force icing out of the decorating tube. As you decorate, continue to roll down the top as needed.
To decorate, place the top, or rolled down part of the cone, in the palm of your hand and apply pressure evenly, with your fingers. Guide the tip of the cone with your other hand.
This guide is from August Thomsen Corp., makers of pure vegetable parchment paper triangles.