As of NS FontAwesome Pro v2 you can insert FontAwesome icons into menu items.

Open up the menu item you wish to add an icon to and click on the FontAwesome Icon tab.

In here you can select the icon from the icon-picker, set the icon color, set the icon size and enable or disable the menu text (useful if you want just icons for menu items and no text).

You may need to add custom css to your template. Because every template is slightly different there's isn't a universal method of including an ability of changing icon color based on pseudo classes (active, hover, focus). We recommend using a browser tool like FireBug for Firefox to determine the classes your template uses and adding the needed CSS to your template.