Don't worry about the details. You will register for classes during Orientation. There will also be an academic open house. Again, don't worry about the details. If you want to place out of intro-level classes in some sciences and foreign languages, or music theory, you will have to take placement examinations during Orientation.
Exams are an hour long.
Again, your Proctor will have all the details when you arrive. The Student Activities Fair is scheduled for the end of the first week of classes. You may sign up for activities then. All students share Smith Union post office boxes. Your post office box will be noted on your Residence Hall Assignment Sheet.