If you have notebooks on your computer that you want to sync with your iPad, you must first place those notebooks on OneDrive or SharePoint. Notebooks created in versions earlier than OneNote 2010 will not sync with your iPad.
On your Windows computer, do the following:
Start OneNote and open the notebook that you want to access from OneNote for iPad.
Select File > Share and choose a OneDrive or SharePoint location for the notebook.
Follow the instructions on the screen.
Note: Before you can access notebooks on SharePoint, you must first use OneNote for iPad to sign in to OneDrive.