Using the DIV theme by Elegant Themes and you may already have the email address and telephone number in the top header, but what if you also want to add whatapp number with the whatsapp icon. This post will explain how to add an extra number with an icon to the top header?

You need to edit the header.php in your theme. please go to your theme folder then edit header.php.

Please fine the line:

<span id="et-info-phone"><?php echo et_sanitize_html_input_text( $et_phone_number ); ?></span>

And paste this line right after it:
(replace "123123123" with your number)