The social media icons in the Footer 3 widget area (on the lower right side of the theme) are displayed using the Web Savvy – Social Widget.
To configure this widget go to Appearance –> Widgets and drag an instance of the widget from the left side to the desired widget area on the right side where you wish them to be displayed.
Then add the full URL (web address) for your social profiles in their respective widget settings fields. Remember to click the Save button to lock in your changes.
If a field is left blank then that icon will not display in the widget on the front end of your site.