There is a small slit in the bottom of each mold that you have to press the stick pretty firmly into to get it to slide in. You want to do this after you've put the ice cream in. I know, it totally messes up all the work you did to smooth the ice cream out, but it's a lot easier to re-smooth the ice cream than it is to put the popsicle stick in first and then try to smoosh the ice cream around it.