Hi Jon,
The glass goes into the weatherstrip first. Next, a cord is wrapped around the assembly in the pinchweld slot of the gasket and finally it is installed in the opening using the cord to pull the gasket over the lip of the pinchweld. Do a search and you will find a lot of helpful hints that will make the install go smoothly. It is a very doable project.
Are you starting out with a good quality new rubber gasket?
