F-1 international students can pursue co-ops and internships by obtaining the Curricular Practical Training (CPT) or Optional Practical Training (OPT) work authorizations.
In general, F-1 students must be enrolled full-time (12 credit hours) for two fall or spring semesters and receive an employment authorization from OIE or USCIS before becoming eligible for off-campus employment. This means that if a student begins their academic program in a fall semester, they will be eligible for off-campus work after attending full-time fall and spring semesters. If a student begins in the spring semester, they must attend full-time spring semester and the next fall semester before becoming eligible for off-campus work.
The two types of off-campus employment are:
Applying for CPT is solely the responsibility of the student and therefore requires no action on the part of the hiring organization. (The employer needs to issue a letter to confirm the co-op or internship offer.) There is no cost to the employer. The processing and approval time for CPT is usually within 5-10 working days.
After the student has been offered and accepted a co-op or an internship, they submit a placement form with the Career Center providing their offer letter that needs to include the co-op or internship start and end dates, total number of working hours, as well as the organization’s name and complete physical address. The student also needs to provide the job title and the job responsibilities. The CPT process is facilitated by the Office of International Education (OIE) in partnership with the Career Center. In accordance with U.S. immigration regulations, students who engage in part-time or full-time CPT must still be full-time students during the academic year. They do not need to be enrolled full-time during official vacation periods (such as summer).
Please see here U.S. Employer’s Guide to Hiring International Students