Find the registration (SIMS) code of the new course or section for which you wish to register. Type it into the Replace With: box. Then click on the Replace button. This automatically drops the original course and replaces it with a new one ONLY if the new section is available. IF NOT, you should still be registered in the original course unless you replace or drop it.

IMPORTANT
You must check your registration to be sure that the right classes have been replaced and dropped.