The Extra Theme allows you to add social media icons / links in the header and footer. If you’d like those links to open in a new tab, you can do so with the following jQuery code:

	$('.et-extra-social-icon a').attr('target','_blank');

You can add this to the theme by pasting it into "Extra > Theme Options > Integration > Add code to the head of your blog", after anything else that is in there.

If you’re not comfortable adding jQuery code to your site, you can use my Divi Booster plugin to configure the social icons to open in a new tab. The setting you need is located at “Extra > Divi Booster > Site-wide Settings > Icons > Open social media icon links in a new tab”.  Divi Booster also allows to add over 160 new social icons to the top header and footer.