In this picture the cupola is being "charged" with coke. The coke will be layered with iron i.e.. coke/iron/coke/iron and so on. At some point a small amount of limestone will be added into the cupola to act as a flux to help the iron flow and isolate impurities.
http://ourworld.compuserve.com/homepages/Dyaros/stlmanuf.htm This web site will give you some more explanation about how iron is made. It is important to understand that steel is cast iron which has been further refined. All steel started out as iron.
This picture gives a better view of the blower forcing air into the cupola.