The reference work must be done using a bibliography found at the end of your work. The Harvard reference dates back to 1881 and is an author-date style. In a nutshell, you should quote the author and the date of the source. The full reference list entry will contain further information, including title, edition, type of material and place of publication.
These are some of the most frequently referenced types of materials. You'll find many more specific examples on our reference templates page, but let's look at the basics for now. Title of the journal, volume (number), page range of the article.