As long as it is an employment, paid or not, you will need employment authorization from Department of Homeland Security if you are in F1 status. CPT is one of them.
CPT is the most straightforward employment authorization you can get as an international student. You will need to register a course which will require an off campus employment as a practical training for the major you study. The course is credited so that you have to pay tuition for it. The international student office in university will give you a updated I20 which includes the employment authorization for the specific employer hired you.