I assume, you have the Haynes manual
. There is a good description.
If not, here it is in short:
You have to set the ignition timing at full advance. This is with the manual
advance-retard cable in slack position ( Sometimes there is a wrong magdyno fitted and it is just the other way - the manual
cable is normally fitted on the left side of the magdyno, on my B33 it was on the right side - was a great mess to work it out).
Then you set the engine in the compression stroke 11 mm before TDC and look, if the contact breaker points are just opening - a cigarette paper between the points slips when the points open.
To measure I put a small allen key in the spark plug hole, mark the positon at TDC and make a mark at 11 mm distance.
To retime the igniton the magento pinion will require removal from the magento armature. Its situated under the timing side cover. To remove the pinion you have to use the correct puller, never think of not using it !!
Refit the pinion, check the timing again, thats it.