The Social Menu contains the social media links for the sites. It is found in the lower-right corner of the footer and displays as a series of social media icons. These icons come from http://fontawesome.io/icons/. The Navigation Label field contains the reference to the Font Awesome icon. To change the icon used, or if adding a new social media channel to the site, just remove the fa- in front of the icon name and use what is left in the Navigation Label field.
For example, to use this LinkedIn icon (http://fontawesome.io/icon/linkedin-square/), remove fa- from fa-linkedin-square. Thus, the Navigation Label field value will be linkedin-square.