When writing out the footnote, use the long version of the citation first and then the short version on subsequent references of the same text (Noodle Tools can create both for you). Note that the page number is included in both examples:
Long form: Richard Dawkins, The Selfish Gene, 2nd ed. (New York: Oxford University Press, 1989), 192.
Short form: Dawkins, 192.
Include a bibliography at the end of your paper that lists all of your sources (Noodle Tools can make this for you).