For your assignment, you are being asked to follow whatever citation style is used by your focal paper. This will likely not be a style you are familiar with, so you will want to pay attention to the formatting of the references and in-text citations.
The good news is that you are not completely in the dark about how to format your references. Since there are so many different accepted styles used in biological sciences, most journals will have detailed information about this in their guidelines for authors. Look for links that say something like "Author guidelines", "Submission guidelines", "Manuscript preparation", etc.
Citation managers are extremely useful tools created to help researchers keep track of all their sources. I highly recommend checking them out as an option, either for this class or another. If you have any questions about them, please don't hesitate to ask.