You can edit the social links in the search nav section by going to Content > Link Lists > "Social Links"

You can edit the name, the link destination, and the icon using the "icon class" field in the link list

A list of icons available on your site can be found here: http://beltway.monkpreview3.com/_assets/fonts/icomoon/demo.html

Once the site goes live, the URL will change to: http://beltway.org/_assets/fonts/icomoon/demo.html

You can edit the additional links in the search nav section by going to Content > Link Lists > "Search Links"

You can edit the name and the link destination in the link list.