This is an electronic process.  Please see https://www.iun.edu/registrar/students/add-drop-course.htm for more details.  If the student is a College of Arts and Sciences student, they need to follow the online process for late withdrawals within the college at http://www.iun.edu/coas/policies-and-procedures/late-withdrawal-policy.htm

Withdrawals during the automatic W period require the approval of the academic advisor. After the automatic withdrawal period, a student may withdraw only with the permission of his or her dean. This approval is given only for urgent reasons relating to extended illness or equivalent distress. To qualify for the grade of W, a student must be passing the course on the date of withdrawal. If the student is failing, the grade recorded on the date of withdrawal will be F.

Students who alter their original class schedules, whether by personal incentive or by university directive, must do so officially by the procedure outlined above. Students who do not assume this responsibility are jeopardizing their records by the possibility of incurring an F in a course not properly dropped or not receiving credit in a course improperly added.

Students who simply stop attending classes without formally withdrawing will jeopardize their student status, will become liable for repayment of all federal financial aid and tuition and fees.