There are many kinds of sources, and what type of evidence will work for your assignment can depend on several factors–your program, the type of assignment, and your instructor’s preference.
Make sure you are clear about this part of the assignment, because your use of sources will be crucial in writing a successful paper. You are not just learning how to argue; you are learning how to argue with specific types of materials and ideas.
If in doubt, ask your instructor what counts as acceptable sources.
You can also ask a librarian for help. No matter what kind of source you use, be sure to cite it correctly—see the Citation Guide.