Well, you could start off by writing a passage or paragraph. See, an essay is split into 5 parts:
Introductory,
3 Body paragraphs (like the meat and the details)
And the conclusion (wrap it all up).
You probably know how to write a Body Paragraph, it's basically writing about a topic and has details and is the main chunk of the essay. Introductory is starting the essay. Basically, you want to hook your reader to reading your essay.
Conclusion is where you bring everything you wrote in the introduction, and body paragraphs, and wrap it up / summarize it.
You could google or ask your teacher to help you with it.
