Whether you are trying to register online or do a class search, the schedule will tell you if the class is open or closed.
If you want admission into a closed class, you must get consent from that professor. The best way to contact a professor is usually via e-mail. To find your professor consult the DePaul Directory. In your e-mail request, you must provide the professor with your name, e-mail address, student ID number and the specific class info (name, number, days and times) as well as a brief explanation as to why you need permission to enroll in the class. If approved, the class will be added manually by the LAS College Office. If you have a financial hold on your account, you cannot be added to the class even if you have permission. It is your responsibility to clear any holds from your account before you attempt to register. You may not be added to classes after the last day to add for the quarter.
There is no guarantee that you will be allowed to join a closed class, but it is always a good idea to ask.