I am borrowing my dad's 10/22 (probably for an extended period, since its only been shot once in 30 years

). By the serial number it was made in 1975. Gave it a good cleaning and its looking good. Shot it when I was a kid but haven't had a chance to shoot it recently yet.
It has a bushnell scopechief 3x-8x which I had some questions about. Obviously the ring towards the eye piece is for zoom adjustment, but how would you zero in this type of scope? There are two knobs on it (shown in picture). Any info about this scope is appreciated. Couldn't find a manual for it on google.