This is the story of a story. Once upon a time there was this story, and the story said to itself, how should I begin?
Try the usual way.
What, in the dark with a man and a woman, in a story that is still to tell itself?
Well, you've got to start somewhere. Say, long long ago... Or, far far away... Or, another time in a different distant country... Or just, once...
That's good. "Far away", so you know the place is close to your own heart. "Once" is nice, so we know that it always happens.
