This is our first incubator and I'm sure this is one of those things that will be obvious to me later but right now we basically have it put together with some parts left over and I'm not sure what to do. We have two semi circle metal parts and some ball bearing that came taped in the box that were not included in the instructions inside. I just watched a video on how to set this thing up and they weren't mentioned. A little slip of paper came enclosed that identifies this as a "Stainless Steel Track Insert" and has some sort of instructions and a diagram, but I can't make sense of it. Where do I put these?