if it's just to replace a faulty dizzy, the short easy answer is just to simply note/photo/mark the exact angle position of the dizzy unit relative to the engine head, disconnect the HT leads and dizzy connector, unbolt & remove the old dizzy, fit the new dizzy in exactly the same angle, reconnect everything.
the longer proper answer requires a strobe light to synchronise the ignition timing on the crank with the ECU 15deg timing at idle.