Navigate to CONTENT > LINK LISTS > "SOCIAL LINKS"
You can change the order the icons appear by using the arrows to arrange them. Click the edit pencil to select a different icon and specify which URL the icon will link to.
The custom icons are created by entering a custo class in the icon class field.
To see a full list of available icons: http://mk030.monkpreview.com/_assets/fonts/mk030/ (substitute your url for http://mk030.monkpreview.com For example, http://www.fakechurchname.com/_assets/fonts/mk030/)