If your administrator has granted permission, you can upload your classes individually by navigating to the green + Classroom button from your class bar on the left-hand side of the screen.
Now, you can choose to either add a class individually by choosing Enter your class name, or import your class from Google.
Adding an individual class will allow you to fill out a webform to simply add a class. If you choose to import your class from Google classroom, you will be asked to link a Google account.