For example: Polybius, Histories 2.24 (L&R I.61). Note that you may convert the Roman numerals that L&R love to use to Arabic numerals (but can retain the Roman numerals if you choose to).
If you’re citing an inscription or other documentary source, simply copy what L&R have:
For example: IG, vol. 9, part 2, no. 338 (L&R I.120).
If you’re referring to Livy book 1 (from the moodle site), cite by book and chapter numbers. For example, Livy, History of Rome 1.8 (referring to book 1, chapter 8).
If you need to cite Potter, use author-date: Potter 2014, 75-77.