Contax Medium Format Cameras Somewhat Off The Mark How Do I Advance Film In A Contax 645 Medium Format Slr?

How do I advance film in a Contax 645 Medium Format Slr? - contax medium format cameras somewhat off the mark

Someone was cleaning his garage and scored twice for an agreement. I have three backups of movies, but can not the film, about the S advance to meet the exposure. I read books online, instant messaging and the use of dark blades ect. Everything can not understand. Has anyone any idea what you do wrong