Think about the purpose of your narrative. Usually, a narrative works as a story. By expressing your interests through the use of narrative, you should be attempting to make others understand your interests. Your story should capture your interests and instil them in others. While creating this effect, a narrative about interests should also help you create an image of yourself.
Choose what to write. There is no specific topic in narrating your interests. It pretty much comes down to you. You should write about what means the most to you and what you feel represents you most effectively. You can write about whatever you want. You might wish to talk about your affinity for dancing and music, how you found these interests and how they make you feel. A narrative about interests serves as a self-exploration.
Get it down on paper. This is often the tricky part, but once you get started, it becomes easy. Begin with the word "I." I am, I was, I feel. Use the paper to scrawl down as many ideas as possible. A narrative about interests is your own story. You are putting your life down on paper. Forget about rules and restrictions. Once you have your life in front of you, gather it, shape it and put it together in a way that says the most about you.