Look for a few Featured Articles or Good Articles in the subject area in which you’re writing, and see how the authors of those article cite sources.
Before you add a reference, you may want to check that there is a section where the footnotes will appear. Look for a section that contains either the <references /> tag or the {{reflist}} reference template, toward the bottom of the page, below the "See also" section and above the "External links" section. If the section does not exist yet, click on the "Edit" tab to begin editing the page and enter this code in the appropriate place:
==References==
{{Reflist}}
There is no single acceptable style for citing your work on Wikipedia, such as MLA or APA style, as may be used in your university courses. You should, however, maintain a consistent style for citations throughout the article. If you are expanding an existing article, all references should be in the same style as what’s already there. Take care to keep any citations previous editors have added to the article. One easy way to keep your citations consistent — and to add citations in general — is to use the citation toolbar.