Go to Databases A-Z, and select a database depending upon your topic.  If you cannot choose one, a good, multidisciplinary database is Academic Search Ultimate.  The Search screen of this database, along with many others, has a checkbox to limit your results to "Peer Reviewed" journal articles.  Other databases may have a similar checkbox of "Scholarly Articles" or something similar.  Check this checkbox and go ahead and do your search.

If you need any further assistance, use Ask Us to get in touch with a librarian.