In a narrative essay you have to have a story to tell. Think of something (perhaps in your own life) that you think people might find interesting. You don't have to start at the beginning, but that is always a good place to start. First, think up everything you can about the story. Then rearrange the words to make it interesting (and readable).
.
I just ran across this one. I think it expresses what a narrative essay is all about. The author tells a story and expresses her feelings about what happened.