Each of us leads a unique life. We are products of our past experiences and no one has a background exactly like ours. Draw from that background. Reflect on what you already know and write it either as fiction, autobiography, how-to, or any other genre you like. Use your already accumulated knowledge and wisdom (and we all have more than we think we do).
But don't stop with what you know. Move into what you'd like to know. Research by reading and asking questions, and learn about topics that grab your interest. For instance, in 1990 and 1995 I co-wrote two books about Antarctica, even though I never went there until 2003. I read widely because of the two books, the first of which was published by a company that specializes in true adventure, and they called it With Byrd at the Bottom of the World. It's the story of Norman Vaughan who was then the last surviving member of Richard Byrd's historic flight over the South Pole. (He went on a ship, disembarked on the icy continent, and a team of men with dog sleds went 400 miles inland. Norman was in charge of the dogs.)
I didn't know much about Antarctica, but I read widely and felt as if I had been there long before I boarded a ship. That's one of the marks of a professional—we're curious people. We want to know more. We don't settle for surface information.
Good writers write what they know;
Good writers explore new areas to increase their knowledge.