Been a while since I did mine but I think I either used the OEM timing marks or a degree wheel and an analog ohmmeter - to see exactly when the points opened. Some use the center /cam of an old flywheel so they can access and set the points more easily.
I just guessed for the first try. It gets a nice spark when spinning the flywheel. It fired once, but then flooded. I'm going to look back into the carb, I have not done one of these either.