Couplers are wonderful to use so that you can use the same bag of colored icing and switch tips. Step 1: Remove ring from coupler. Step 2: Trim narrow end of plastic bag, a little at a time, so that 2 or 3 threads will protrude from bag when coupler is pushed down into bag. Step 3: Push coupler down into bag securely and place decorating tip over end of coupler. Step 4: Screw plastic ring over decorating tip onto coupler to hold tip in place.