writing help?

I have to write a story for school, the story is a continuation of
the movie John Carter, i don't reallt have any ideas on what to write,
so far Ive only written `"Ak Ohum Oktay Weez... Barsoom."

After ten grueling years, he was finally back. He looked around and saw he was
right outside Helium, he rushed in ecstatic by the thought of seeing
Dejah again`

any ideas or tips on how to write better would be great