Go back in time and do something that will make a significant change.
While it most likely wouldn't create a parallel universe, it would create a parallel world or time line, though an unnatural one.
Although the concept seems stretched or far-fetched, in biblical context it becomes more valid.
There are numerous prophecies regarding end-time, latter-day scenarios and events. There are only several ways to account for the origins and the fulfillment of the prophecies.
1) The prophecies were a stated desire and outcome that necessitates a careful control of events to order their actualization.
2) The prophecies were actual accounts of first hand observations conveyed from the future or present to the past.
In all likelihood both premises hold weight, although the second is more plausible. But once stated it may well bring the first premise into play in order to avoid a false prophecy. For interaction with the past can initiate change and it's possible that change can invalidate future events.