Steps to use headings created in layer symbology to organize your legend. Each heading can be used as a separate legend item.
Make sure the layer has headings.
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.
Double-click the legend to open the Legend Properties dialog box and select the Items tab.
Select the General tab.
Choose a heading from the 'Only show classes from this heading' dropdown list.
The layer and heading are now in the Legend Items list. Additional headings can be added as new legend items in the same way.