In step 14 you make something, well step 15 tells you to just fold back up the thing you did in 14 but only half way, not to the very top just as to make it perpendicular with the rest of the model. You might be getting confused since step 16 is looked from below
The only tip I can give you is just to do what is written. It´s easier if you place the little square on the bottom on a hard surface like a table, then open the upper part slightly while twisting the layers around. Everything will pop into place by itself once you try.