First, go to Dashboard => Divi => Theme Options:
Next scroll down almost to the middle of the page until you see the social options:
You’ll want to make sure that you add a link to your social field and that it’s enabled (meaning it’s set to be displayed on the front end of your site). When you finish, click Save Changes.
Now go to Dashboard => Appearance => Customize => Header & Navigation => Header Elements. And make sure you check the SHOW SOCIAL ICONS option and click Save:
Now the icons will be displayed on your page.
Also check: How to Add More Social Media Icons to Divi