Steps to use headings created in layer symbology to organize your legend. Each heading can be used as a separate legend item.
A. Right-click on the layer in the Table of Contents and select Properties.
B. Select the Symbology tab.
C. Make sure the layer is symbolized by Categories.
D. Right-click on a category’s Value, Label, or Count field.
E. Choose Move to Heading > New Heading, to open a dialog box to name the heading.
Or, select Move to Heading and select an existing heading in which to put the category.