There should be:
1. A shutter cocking lever
2. A shutter release ("trip") lever
3. A pin right above the shutter release that moves to trip the shutter via the left hand trigger grip
4. A manual switch to open and close the shutter for ground glass viewing (or T exposures). This is what the instructions you posted are talking about.
5. An aperture selector lever
Are you sure that you have not got number four engaged (pulled out)? If you did, the shutter would be open no matter what you do with anything else.
This is not the camera to devote important film to if you do not even know what a leaf shutter is yet. It is 100% manual without a single interlock. It is just like a large format camera except for the film it takes. You must cock the shutter after each shot. This is true of all cameras, however on this camera everything is not taken care of simply by advancing the film, like with a 35mm SLR. In other words, you have a steep learning curve ahead of you before using the thing on an important shoot. However, once you learn how to use the camera, you will understand all cameras better, and have superb results. I suggest a basic photography book like "Photography" by London and Upton, or "the Camera" by Ansel Adams, and also an invaluable book called "Mamiya Systems Handbook", by Robb Smith. It is a great book covering Mamiya twin lens, Press, and RB systems, plus has sections on general photographic basics.
I was i the same boat as you, as a Super 23 and a Graphic View II were my first cameras other than 35mm, shortly after I started shooting. I understood the mechanics of operating a manual leaf shutter from using the GVII, but my big mistake was that I started shooting with my 100mm lens in the collapsed position, which is where it should be if you are using the camera's rear movements, and at no other time. I figured that the rangefinder was way off, so spent $140 to give the camera a CLA that it didn't need. DUH!!!
Oh yeah. To advance the film, you must first hit the release switch of the advance lever. Then (very important), you must know that one stroke of the advance lever will not advance the entire frame. you have to keep advancing until it stops. The film transport is in NO WAY connected to the shutter like with a 35mm SLR, so if you do not advance the film all the way, you can shoot over what you just shot, and then two shots are toast.