First you have to articulate a theory of yours as to why people do the things they do (psychoanalysis, for example), or why the world is the way it is (Marxism, for example), or what the function of art is (Moral Criticism, for example), or what the right way to read a piece of literature is (Reader Response, for example). I imagine that this theory of yours is one that you have had for some time, but if you want to divine something for the sake of this paper, feel free to do so.
Then, choose some of of the books, or plays, or short stories, or poems, that we have read in class this semester that provide evidence for your theory's validity. Use many examples from the texts, quoting them often and explaining your quotes, to validate your theory. You may also use other sources as appropriate (other texts we have not read in class), but you must talk about at least one of the texts we read in class in depth and detail.