to focus on the ground glass you are essentially using the camera as a view camera -- this is not the camera's primary design, but it can easily be done.
Put camera on tripod.
Open camera and extend lens to infinity stops.
Crank front shutter open -- either set it on "T" or "B" or there is usually a way to open it after you cock it. Many shutters are different, so you have to figure this out yourself.
Set rear shutter to "O" for open.
Open rear focusing hood and you should see a fuzzy inverted image. It helps to open the shutter diaphram in front wide open. Put a cool black cloth over your head and wrap it around the camera so you can see the image.
Focus.
Close whichever shutter you are going to use. If you intend to use the rear shutter, leave the front shutter open, wind the rear shutter to the speed you want. Set the lens opening up front.
Insert film. Remove dark slide.
Take picture.
Put dark slide back in. There you are.