It should be obvious but sometimes isn't: Facts are basic to nonfiction writing. Even a personal essay or memoir relying mostly on the author's memories gains power by using "hard facts" from other sources: photos, reports, quotations, definitions, dates, and interviews. Maps, court records--facts are everywhere, and readers need them to fully enter the world of your essay. But surprisingly, writers of personal essays often don't think to mention what year they are recalling, what town they lived in, the names of their parents and siblings, the name of the rival school (Hamilton? Franklin? Something like that. Does it matter? In nonfiction, yes). They often neglect too even to describe themselves, as they were or as they are.
Some writers arrive at creative nonfiction thinking "creative" means "no research." (After those college research papers, what relief!) But even if you don't use all the facts you find, the ones you do use give your personal essay muscle and traction. Did "your father read books", or did the shelves he built in your basement overflow with his personal library of 200 Civil War biographies and histories? (Research the family photos! Open the old boxes!) Did "your family go to church," or did you and your mother and older brothers Allen and George take a slow-moving city bus every Sunday to the First Christian Church on Maple Street? (How far was it from home? How much was the bus fare? Interview your mother, or look those up.) Trying to recreate your reality in your nonfiction? As you revise, find and share with your readers the facts of who, what when, where and why.
Do it too for yourself, just to own your own facts. It feels like owning gems.