Your class will become available on the first day of the semester.
If you try to log in before the first day of the semester, you'll notice that your classes are not available. In general, online classes are not available until the firstofficial day of the semester.
You can check the Academic Calendar for an overview of the start and stop days of the current semester. Your class may have different start/stop days; you can look up your specific class in the Schedule of Classes.