I'm not sure that any e46's had a touch screen NAV unit - but I could be wrong.... The scrolling is accomplished via the right hand knob on the NAV unit, I don't have mine here with me or I'd run out and do it really quick. I believe that it is in the 'menu' section of the NAV options, again not 100% - it won't be in the main manual, it is in one of the additional supplemental books/manuals, they don't typically supply them with the purchase of the car unless that car is equipped with all the appropriate equipment.
"! First rule of Italian driving, that which is in your mirror is not important !"