If you cannot find a teacher's class listed in your OneNote notebooks:
1. Go to your school email and look for an invitation like this one:
2. Click the link in the email
3. Once the notebook opens in the browser, find the OneNote app on your iPad and open it
4. Click the < arrow towards the left of your screen to view your notebooks
5. If you still don't see your notebook, click More Notebooks to see a list of available notebooks and click the needed notebook