The airbox sits directly behind the tank in front of the battery. There really isn't a side, pretty much in the middle. On my 550LTD there is a knob, this one looks like the throttle cable comes down in the center but no knob.The screws your book is talking about are the mixture screws, you don't want to mess with those. The idle adjust is a large knob you turn with your fingers. It's between the carbs on the bottom and you reach it by going under the carbs on the airbox side.