MLA style is most commonly used in Humanities disciplines such as English and Comparative Literature. There are many sources online for MLA style (including Dartmouth's Sources handbook and the Purdue OWL MLA Guide) but the MLA Handbook (9th edition) would be considered the definitive source for resolving any questions around MLA citation style.
Generaly, MLA style uses in-text parenthetical citations with a list of works cited. If your instructor requires you to use footnotes or endnotes, consult Appendix B of the MLA Handbook.