Right click the space after the punctuation mark of the sentence you wish to cite. Then, choose "insert footnote" or "add footnote." The command varies between word processing software, but all major word processors offer a footnote function in the top menu bar, under "Insert" or "Formatting." The software inserts a number and takes you to a box at the bottom of the page to begin the text of the footnote.
Write the full name of the author, followed by a comma.
For example: David Smith,
Follow the comma with the name of the book or article. If citing a book, underline the title or write it in italics. If citing a journal article, put the name of the piece in quotation marks. Follow the title with a period.
For example: David Smith, "My Life as a Graduate Student: A Rope of Sand."
Write the publishing information in parentheses, without a period. Include the city of publishing, the publisher, and the date the piece was published. If the entry is from a journal, include issue and volume number. Follow this with the page or pages from which you are taking the information, followed by a period.
For example: David Smith, "My Life as a Graduate Student: A Rope of Sand."
(New York: Journal of Graduate Studies, Vol. 1, Issue 4, 1995) 45.