Research background material to narrow the focus of your topic, either at the library or on the Internet. Make sure the subject of the narrative is not too new to have enough information to adequately cover the topic.
Ask yourself questions about the topic. Use the journalist's tools of who, what, when, where and why to answer questions about your narrative. Limit your topic to a specific person or group, or to a particular aspect of the topic. Try narrowing your focus to a set region or period of time. Ask why a proposed narrative is important to your audience. Who will it benefit by what you write? What will it change if you write on this subject? Once you have asked these questions, choose the specific characters, settings and subject matter you want to write about.
Compose a limited topic question based on your research. This question should address the purpose of your narrative. Compose a theme or thesis based on the question. Write an outline of the points you want to cover in your narrative, then begin writing based on the subject headings of that outline.
Add all components of the narrative structure to your focused narrative. The plot should include an introduction, actions rising to a climax, the consequences of the climax and a resolution to the conflict or premise. Narratives need to have sufficient detail so that the reader is seeing, hearing, smelling and touching what the characters are, but not so much that the reader loses interest or becomes confused. Allow the reader to use her imagination when reading your narrative. Too much detail can rob the reader of relating her own experiences to what you have written.