OneNote 2016 for Mac keeps all of your notes in the cloud by automatically syncing them to your OneDrive account automatically. This lets you view and edit your notes anywhere on all of your devices.
While you cannot turn off automatic syncing of notebooks, there may be times when you want to sync manually, to force syncing a large amount of changes to notes before having to disconnect on short notice (for example, when stepping on an airplane).
Do the following:
To see your list of notebooks, if the Navigation button is off ( ), click the Navigation button to on ( ).
Click the Notebooks list dropdown arrow that appears above the section and page lists. You may need to click the name of the current notebook to see the list of notebooks.
Hold the Control key while clicking the name of the notebook you want to manually sync.
On the menu that appears, click Sync This Notebook.