If there are no assignment submission folders available to submit to, the instructor has added a start date that has not yet happened and/or an end date that has passed.
Check the due date of the assignment you want to submit to the Assignments submission folder. If the assignment is not due yet, check back closer to the due date. Alternatively, if the assignment is late, contact your instructor with any further inquiries relating to late submissions. If you believe that you should have access to the Assignments submission folder, contact your instructor.