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Handgrip rewinder install? There is no rewinding functionality on the handgrip, if I understand you correctly.
Did your camera come with the grip? This is just a grip for holding the camera. To install it, turn the shutter speed ring to B (bulb), and then twist it a little further, as you insert the grip. It has three positions, which you can set by pressing the little chrome button on the inside of the grip, while turning. The rearmost position is most comfortable unless you are doing something unusual. I shoot without the grip sometimes, it also works fine like that.
Once you have the battery charged, slide the film back slide from the top to the bottom. This is the bar which straddles the rear of the film back. The camera will only release when the film back is open, i.e. the slide is at the bottom. The mode wheel around the shutter speed ring will move more lightly if you press it in slightly while moving it to S (single shot). Then if you have set a manual shutter speed and manual aperture, it should release.