If the dizzy is out of motor, set up TDC on left cyl, turn rotor to LH sensor, line up lines on sensor & rotor. Slide in dizzy watching how far rotor rotates, pull it out, rotate rotor the distance it moved back that amount.
Slide in dizzy, marks should line up close enough to time the bike.
If dizzy is in motor and you are installing Dyna 3. set up TDC on LH cyl, install rotor so marks on rotor and sensor line up on LH cyl. This will be close enough to time the bike.