Here, briefly, is how the MLA citation system usually works. (See MLA-4 for more details and model citations.)
in-text citation
Bioethicist David Resnik emphasizes that such policies, despite their potential to make our society healthier, “open the door to excessive government control over food, which could restrict dietary choices, interfere with cultural, ethnic, and religious traditions, and exacerbate socioeconomic inequalities” (31).
entry in the list of works cited
Resnik, David. “Trans Fat Bans and Human Freedom.” American Journal of Bioethics, vol. 10, no. 3, Mar. 2010, pp. 27-32.
This basic MLA format varies for different types of sources. For a detailed discussion and other models, see MLA-4.