Select the component representing the tab (typically a JPanel) and go to the Layout properties tab in Inspector. You can set tab title here, as well as tooltip and icon. For example, step through the following procedure.
- Create a new JFrame.
- Drop a JTabbedPane component onto the JFrame in the Form designer window.
- Drop a JPanel component onto the JTabbedPane. A tab will appear.
- In Inspector select the JPanel, then click the Layout tab for the JPanel.
- The Tab Icon, Tab Title, and Tab Tooltip properties will be exposed, and can be modified.
Source: NetBeans User FAQ