Your sources must be cited using any "appropriate format for the Humanities or Social Sciences".
Your instructor recommends the MLA System: Parenthetical Author-Page References (humanities).
Additional styles in the Humanties and Social Sciences are listed below.
Consistency is important. Once you have selected the style continue to use it throughout and always use the latest edition of the style guide. You should not use different editions of the style guide, so be careful if you find a guide on another site to check the editions.