Well, if you want to write your own story to change history, start with a 'what if' scenario. Let's say you're interested in World War II. You could write a story where a certain diplomatic negotiation went differently, preventing the war from starting. You need to have a good understanding of the historical context. This means researching the political, social, and economic factors at play. Then, build your characters who will be the agents of change in your story. Make their motives and actions drive the change in history you envision.
One way to write your own story to change history is to look at the small, overlooked details of a historical moment. Take the Civil Rights Movement in the United States. Instead of focusing on the big - name leaders, you could write from the perspective of an ordinary citizen who took an extraordinary step. Maybe a young person who started a small, local movement that had a ripple effect. Incorporate real historical facts into your fictional account. By doing this, you can show how individual actions, even those not widely known, can have the power to rewrite history in a sense.