Click the home icon at the top left-hand corner of your screen if you're not already on your homescreen. Once on your homescreen, click the "Create a New Planbook" button, give your planbook a name, and then select the right school year/term. Finally, click “Create it. I’m ready to start planning!” to add classes and continue setting up your schedule.
Note: It's a good idea to make just one planbook for all your classes per term (i.e. semester, trimester, or year). Otherwise you'll have to switch back and forth between planbooks whenever you plan.