An outline is a way to organize your information into a series of well-ordered and coherent thoughts. You may also find you’ve got some holes in your outline. Better to find out now than when you start writing!
Use the outline to give yourself a better idea of what your paper is going to look like, or needs to look like, with the right sources.
Your outline doesn’t have to be a traditional one if you don’t want it to be. (Unless your professor wants to see it.) It could just be a series of notes. Just be sure that those notes form a coherent writing strategy. That’s what an outline does.