Select a feature from a plan and the feature details menu will appear on the right
To change the use, click on Assign Use Change
A list of available uses based on the plan type and feature you select will now be available.
From select a feature you can search for a particular use or expand the available menus.
Select your use and this will update the assignment.
Note: Unless you change the name, the use you assign is what appears in the legend when a map is printed.