A full list of available icons for your site can be found at https://fontawesome.com/v4.7.0/icons/.

Once you find the icon you want to use, click that icon and copy the class to use in that icon class field.  eg. Selecting the Facebook icon will yield the class "fa-facebook"

Additionally, you have some custom icons that you can use on the site. They are:

• icon-custom-first-things-outlined
• icon-custom-first-things
• icon-custom-group
• icon-custom-serve