When authors submit manuscripts for publication, the "citation style" is dictated by the publisher. The most common formats are variations on "numbered" and "author-date" styles. When formatting citations for a course assignment, your instructor may specify which citation style is required, or else they may let you choose.
For written assignments, it can be helpful to use a "numbered" citation style, such as the one used by Biochemical Journal. One advantage of this approach is that the reader can easily see how often the writer is repeatedly citing the same source.
Another common approach is to use an "author-date" style, such as the one used by Journal of Biological Chemistry. An advantage of this approach is that the reader can easily see how recent your cited sources are.
If your instructor has not specified a preferred style for your assignments, you can find both of these options within your citation manager "Styles" options.