It sounds like you have a Graflok back. It is possible to remove the groundglass panel and use the Graflok slides, and necessary to do so for the "humpback" style rollfilm holders, but with an ordinary sheet film holder you can leave the glass in place and just lift up on the right side of the back with the back oriented in the horizontal position and slip the holder underneath the glass. The spring tension of the back will hold the holder in place, and there is no need to use the slide locks or remove the glass.

This is such a basic thing, common to virtually all large format cameras, that I'm not sure it's covered in the Crown Graphic manual, but you can go to www.graflex.org and see if they have an illustrated manual showing how it's done. If not, you might get a copy of Steve Simmons' book, _Using the View Camera_ for a basic introduction.