Literary and film scholars closely read, rigorously analyze, and deeply think about their primary sources (i.e., literature and films) to develop new ideas and arguments about a topic. However, scholars do not work in a vacuum. When writing a scholarly book or journal article, they take their original thoughts and put them in conversation with other scholars. They use other scholar's work to:
Some scholarly conversations have a long history (e.g., criticism of Faulkner's works). As a beginning scholar, you need to survey the literature to see how your thoughts fit into this ongoing conversation. Other conversations are just starting (e.g., criticism of the latest zombie movie). In this case, you may not find scholars discussing your specific primary source. Instead, you would need to think more broadly about analogous examples and see how the arguments scholars have made about those examples could be applied to your object of analysis.