The nature of any good story is not so much its ability to get me to believe it’s true, but it’s ability to get me to suspend my belief that it’s not.
Tom Cruise would never survive jumping out that window and no car could ever make it through the first crash of any chase scene. Harry Potter doesn’t really have a magic wand and fish can’t really talk. But that doesn’t matter. It only matters that while I’m watching it on the screen or reading it on the page, I believe it. I can root for the hero or against the villain even if my mind knows none of this stuff could happen in real life. I just need to believe it in the context of the story. And most of the time that means I’ve got to suspend my disbelief.
So first, I must create a plausible story with real characters in a world I can believe, even if I know it’s not true. At this point, ‘truth’ is irrelevant. What matters is the story.
This is what you will do in your story; you will create characters and a plot that, while not being necessarily true, will be ‘based on’ real people and events and will, most importantly, serve the purpose of the Story.