You need to make sure you cite your sources. While APSA is the standard citation style in the discipline, your professor is allowing you to use whatever style you are comfortable with as long as you are consistent.
If you need assistance with citations, ask a librarian or visit the citation guides online.
The library's databases can help you identify appropriate sources for your student-led discussions and group projects. You'll notice that we have nearly 300 databases and that some of them have a narrow disciplinary focus. Here are a few recommendations to help you get started:
For a good idea of what databases are generally available in the international relations field that interests you most, use the "All Subjects" dropdown menu on the library databases page to select a discipline (e.g., "Political Science")