When you write a paper that interprets literature, you will need to draft an introduction that announces your interpretation. Throughout the paper, you will need to support your interpretation with evidence from the text. As you do so, it is important that you avoid spending too much time summarizing the plot.
Because literature papers are different from other sorts of college writing, you need to pay careful attention to conventions of literary papers. As in all academic writing, you will need to cite your sources properly, following MLA style.