Do your research making note of the basic information for your sources. This will include author name, article title, year of publication, publication title and publisher.
Locate the areas that need citations. If you quoted or paraphrased from a specific document, cite the document that provides the original information at the end of the sentence. This includes the author, year and sometimes the page number. MLA style looks like this: (Smith 345). APA style looks like this: (Smith, 2004, p. 345) and Harvard style looks like this: (Smith 2004, p. 345).
Check your citations to ensure the full information on the document is included in the bibliography at the end of your paper. Also check against your notes to ensure your information is properly attributed.