How-to Use a Pastry Bag
Secure the frosting tip and coupler on the pastry bag. Place the tip of the pastry bag in an empty tall glass. Fold the wide opening of the bag halfway over the glass. Use a spoon to transfer frosting to the pastry bag. When it's three-fourths full, pull the sides of the pastry bag up over the frosting. Remove the bag from the glass, twist the open end to close it and apply pressure to the bag to pipe frosting on the cookies.