How can I write a narrative on the topic of: A rock star comes to your school and you interview him and be his guide for the day?I was thinking...

A narrative is written as a story.  In other words, you
are telling a story rather than writing an essay.  A story follows a typical format:
exposition, rising action, climax, falling action and
resolution.

In the rising action, you introduce the
characters, setting and initial conflict.  This would start out with you describing your
school day, how the rock star came to be at the school and how you came to interview
her.  The conflict might be that you are very nervous about meeting this person, and
worried about how you will get her safely around the
school.

In the rising action, events develop around the
conflict.  This is where you would meet and describe Katy.  You also make motions to
solve the conflict.  For example, you might have Katy wear a disguise so no one knows
who she is and she can get around the school without causing a mob
scene.

In the climax, the story makes some kind of change. 
This is the most interesting part of the story.  Let's say you are interviewing Katy, no
longer in disguise, and someone sees her through the window and shouts that she's
there.  Now the story changes, because everyone knows that the rock star is there.  What
do you do?  Either way, things can't go back to the way they were before.  This is what
makes it the climax.

The falling action is where you
resolve the big conflict created in the climax.  For example, you may get the principal
to call an emergency assembly and interview Katy in a controlled setting, in front of
everyone.

The resolution is the ending of the story and the
solution to the problem. In this case, Katy will leave and life will probably get back
to normal for you.

Those are just suggestions, but
hopefully they will get the creative juices flowing for you and get you
started!