The Divi Theme comes with an option to add some social network icons to the top header and the footer. However, the set of icons is quite limited. Third party plugins such as my own Divi Booster plugin add lots more icons covering most of the main social networks. But what if your niche social network isn't covered?
One way you can add your own custom icon is to replace the icon of one of the built-in social networks with your own image file.
To do so, pick one of the built-in icons you aren't using and add that icon to your site along with the link URL for your profile / social network page. In this example I'll be replacing the Google plus icon.
Then add CSS similar to the following:
Related Post: Adding CSS to the Divi Theme
You should replace the URL used in the code above with the URL of your own icon file. If you don't have a URL for your file, upload it to your WordPress media library and it'll generate one for you.
If you're replacing a different icon, you'll need to replace each instance of ".et-social-google-plus" with the class name of the icon your replacing.