1. Log in as explained under "CATS Link" and click on "Academic Information."
2. Click on "Add/Drop and Schedule Adjustment."
3. Select a term (if necesary) from the pulldown menu and follow instructions.
4. You will need the 5-digit CRN for each course you wish to add or drop.
Drop/Add on Banner Self-Service (Schedule Adjustment) cannot handle any adding of a course when the course requires permission or when some exception is involved such as allowing a junior into a course restricted to seniors. That's true even if you have permission from the professor; all such permissions and exceptions must go through the Registrar's Office.
Banner Self-Service also will not allow dropping a course after the end of the first week of a semester. That constitutes a late drop, for which there is a late fee; after the first week, all drops also must go through the Registrar's Office (although no signed permission is required).
Please note that dropping (or adding) a course requires more than simply notifying the professor.