Is this the one with the flower that slides down and tightens??
When putting on a step in harness I always lay it on the floor so its making the "triangles" and put one foot in each "triangle". I'm guessing with the Lil' Pals one you would then slip the leash part over her head and tighten it with the flower..
Did you buy it locally?? If so maybe they can help you put it on if your having trouble with it