Can anyone please tell me the best way to cure a 10 gallon, CAST IRON , stew pot?

I want to cook a small stew but my stew pot has been sitting in my shed for 10 years and is really rusty and dirty. Can anyone please tell me how to cure my 10 gallon CAST IRON stew pot so I can use it. An yes in case anyone wants to ask " I will be cooking it outside over and open fire".