If you need to customize menu labels, you do that with wordpress Custom Menus.
You create you menu in Appearance > Menus, then you can open each menu item and place whatever HTML you like in its label.
Know that Xtreme already includes Genericons that you can easily use. Check the help file for how to do that.
Help extract:
To insert one of any of these icons into your content, follow these steps:
- Enter “Text” mode in the WordPress page/post editor.
- Visit the Genericons Site.
- Click on the icon you want to use. This will display information about the icon at the top of the page.
- Click the “Copy HTML” link, and copy the HTML code that is displayed.
- Paste that code into your content wherever you want it to be displayed.