The social media icons are rendered via the FontAwesome for Menus 5 plugin; looking at the source of your page my guess is the plugin is missing or not activated (it should have come with the one click install).
Look under the Plugins in the Dashboard and see if this plugin is listed. If it is there, but not showing as active, click activate.
if it is not there, you need to download the Zip file for this plugin from
GitHub - cogdog/font-awesome-5-menus: WordPress plugin for adding Font Awesome Icons to Menus (use the green “Clone or download” button) and then install by uploading to WordPress in the Plugins area (Add New, then Upload).
The theme documentation tries to explain how to select the icons
Hope that gets your icons lit up.