I would amagine you are talking about setting your third axis

install the sight on the bow
what you do is barley loosen the screws on the pivot screw and the stationery screw.
find a door that is plumb at the jam end and set the upper and lower limbs on the jam this way you know your bow is setting plumb then simply set the third axis until the bubble reads level then tighten the screws back up.
Clear as mud?[8D]