Within the list, select the green "+" to add more items, and the pencil icon is used to edit each one. For your social links, the following fields are used:

• Name: for internal use
• Link: add the URL for your social site. The "enter a URL" option will need to be selected before pasting in the link. The "open link in new window" option is recommended when linking out to another site.
• Icon Class: displays the icon. The custom icons can be created by entering a custom class in the icon class field -> ie: icon-twitter

A full list of available icons can be found at  http://mk037.monkpreview.com/_assets/fonts/icons/ (use your domain when your site goes live).