General in-text citations like Lauren suggests will almost certainly be sufficient, particularly for a short, informal paper. However, if your paper is longer or a more formal paper (for example, a report as opposed to a shorter research essay), a little more rigorous citing may be in order. But never fear, it's easy to do this.
Some high schools even have their own citation guides! For example, Soquel High School in California has put up this citation guide:
Author. Title. Place of publication: Publisher, Publication year. Print.
Welch, James. Winter In Blood. New York: Harper & Row, 1974. Print.
... and Mount Vernon High School in Virginia has posted a PDF table that seems to be a summary or modification of relevant APA citation styles.
A web search on your high school, or perhaps comparable high schools in your area, may yield useful information.
If you find nothing useful like this, your school library may well have a copy of an appropriate general style guide. These have information on citation styles, and really are quite simple to use. There's a question here on Writers - What are the most common style manuals? - that will give you an idea of what style guides are good for what kinds of papers, but any style guide will probably do the job. (APA or MLA, or maybe Chicago, would probably be fine.)