This is a tough assignment. I can only offer a few suggestions to hopefully get you started.
First, you ought to tell what the book is about and not assume that your reader has ever read it. Your description and synopsis should include a little information about Jules Verne himself. You could mention that he was one of the first science-fiction writers and name some of his other works, such as Twenty Thousand Leagues Under the Sea.
Then you might describe your own reaction to the book, focusing on what you liked and what you didn't like. You might have found it a little old-fashioned. If you know of other students who liked the book, you might mention that fact.
Then, since Verne was one of the first sci-fi writers, you could point out that he had a huge influence on all the other sci-fi writers who came after him, right up to the present day. And you might name a few of those modern writers and their works.
As a last suggestion, you could maintain that Journey to the Centre of the Earth ought to be introduced in school because it is interesting to young readers like yourself, because it is very well written, and because it has had such a powerful influence on sci-fi and fantasy writers all over the world. Many of the accomplishments of modern scientists, such as space voyage and undersea exploration, were first imagined by creative writers like Jules Verne.