Set the engine at the base timing that you want for the dizzy...14* is a good start on a Windsor. Point the timing mark right at it on the damper.

Make sure the dizzy is pointed at #1 port on the cap.

Turn on the ignition key and hook a grounded spark plug to the coil wire. (make this by soldering an alligator clip to a spark plug and clamping it to an intake bolt).

Turn the distributor by hand until the plug fires. That will be damn close to the 14* on the damper.

Reset and fine tune with a timing light.