If you need to change your section and the instructor gives consent, your section will be changed and there will be an announcement here.
In this case, you must attend to the lectures of the section you want to transfer to, and you should write your name on the attendance list of the section you will transfer to.
Student C is registered to section 2, but needs to transfer to section 3. She should talk to the instructor of Section 3 and should attend the lectures of Section 3 and write her name and ID number on the list of Section 3. During the add-drop week, the transfers will be done by the coordination, Student C does not need to do anything else.