If you are finishing your degree and graduating after the current semester, congratulations!
If you are not graduating, it is time to begin selecting classes for next semester. Email your academic advisor if you have questions or would like to set up an advisement meeting.
To find out when you can register, consult the registration schedule on the Records office webpage. The link to the schedule PDF is near the bottom of the page under Registration Schedule.
If a class has no available seats, you can choose another section or course, or ask for permission to be added to the closed class. You will need to email the course instructor to ask for permission.
Email your advisor when your proposed schedule is on Self Service. They can review it so you can register when the time comes.