How to edit the menu description
WP Admin > Appearance > Menu > Your menu and expand the menu item.
If you don't have this menu item feature, activate it from the "Screen panel". Check the following screenshot:
The "Menu Pro" Live Composer extension come with more many options. Go to WP Admin > Appearance > Headers/Footers and edit in Live Composer the "Header default". Open the menu module for a full customization options panel.