If you are struggling to get a working schedule for fall (i.e.: you’ve tried several times to rearrange your schedule to use open sections of classes, but have not been successful), you can petition the appropriate academic department to add a full section of a class. The contact information is at the link below. It is not always possible, but they will do what they can to help you.
You also have the option to wait a little bit to see if a section opens back up--sometimes fall schedules need to adjusted after people see their spring grades...and sometimes schedules change because students take classes in the summer which cause changes to their fall schedules.