Within each tab on the OneNote 2013 ribbon are different groups of commands. For example, the Home tab has six groups: Clipboard, Basic Text, Styles, Tags, Email, and Meetings. Commands of similar purpose are grouped on a tab to make locating them easier. You can create a new group on any tab, not just tabs that you create yourself. Create a new group so that you can place commands in it later on.
If you no longer need a group, you can remove it from a tab. When you remove a group, you remove its buttons, as well. You can remove any group, even a default group.
Right-click anywhere on the ribbon. On the shortcut menu that appears, click Customize the Ribbon.
In the Customize ...