Fertilised eggs for hatching can be bought from specialist suppliers. If you have your own hens and a cockerel then you will have ready access to fertilized eggs. It might seem natural to leave the hen to do the work of incubation but some hens have had the inclination to nurture eggs bred out of them leaving you to do the work. Newly laid fertilised eggs will carry on developing even if they are not kept at a steady warm temperature so they need not be collected immediately. The fertilized egg layer will be the broody hen. Test for broodiness by seeing if your hen will settle on eggs or egg like objects (a golf ball will do). Egg incubators should be used from about 6 days after the eggs were laid. The eggs should sit at about a 30 degree angle in the incubator and the shells must be kept every clean. This allows oxygen in and carbon dioxide out. A sophisticate incubator will turn the eggs three times a day. If not you must do this yourself. The more times you turn your eggs the more likely you are to achieve live chicks.
