Go to orientation events. Very likely several people are more scared than you are. Go, especially if you are a commuter student listen to the academic advisers, but remember they are human and can make mistakes. If you need to take placement tests, take them. Once your class schedule is set, walk your schedule so you know where all the buildings and classrooms are. Yes, you CAN change your classes and sections of classes. Go to library orientation sessions the first week.
Since classes start TODAY at the University of Oklahoma Norman campus, you already are too late. The stadium lights have been blazing every night for the last 2 weeks. The heat indexes are high, but I've seen them higher.