Customizing numbered lists - Microsoft Word 2016 - OfficeToolTips I. To create a custom numbering format, do the following: 1. On the Home tab, in the Paragraph group, choose the Numbering button: 2. In the Numbering list, click Define New Number Format... item to display the Define New Number Format dialog box: 3. In the Define New Number Format dialog box: Number style - Specifies the numbering style that ...