Hi Bob ~ darnit, I probably never put index marks on those rotors for you. (I may have.. though)
Looks for a little divet on each rotor that I might have made with a small drill bit - it'd be near the edge. If you find those, then they should line up.
If they are not there... there are two possibilities with 12 magnets and 4 studs, you either get it dead right, or dead wrong (90 deg off). If it's right, the rotors will attract one another, if it's wrong - they'll be in repulsion. There are only two possibilities though...
You can also check with a magnet and make your own index marks. The same pole of any magnet should attract to a magnet on one rotor, and repel the magnet that lines up on the other rotor.