I have a friend who was nice enough to donate her old diaper genie to me. I bought a refill for it but can't figure out how to install it. It has two directions but it doesn't help me. I pulled the plastic up and made a knot and tucked it down through the middle, then I put in a diaper and shut the lid. I turned the handle and opened the lid and the diaper was still there and not twisted. I closed the lid and turned it a few more times but nothing happened. What am I doing wrong? Also, what is the button on the top with scissors on it?