They have to hatch in the incubator and also to remain there for up to 24 hours in order for the last to hatch to have a chance to dry off. During this time they don't need food or drink as they are still nourished by the remains of the yolk. Opening the incubator too soon will let in cold air and reduce the humidity which is needed for the latest chicks to hatch. When egg turning stops, a day or so before the hatch, you should increase the humidity and line the floor of the incubator with soft cotton cloth, or a J-cloth, to give their feet something to grip on, as their leg muscles are not developed at first and sliding around on a slippery surface can cause a condition called spraddle leg. Get their brooder ready before the transfer from the incubator, and initially have it at the same temperature as the incubator to avoid thermal shock, gradually reducing the heat day by day as they begin to grow.