Change link of Custom header/logo image

Edit the Page Template in your theme that outputs the header image to add this link.

This is what I see on the Page Template on my theme

<?php
/**
* PAGE
*
* This file meets the WordPress template requirements for ‘page.php’
*
* @package PageLines Framework
* @since …
*
* @link https://www.pagelines.com/
* @link https://www.pagelines.com/tour
*
* @author PageLines https://www.pagelines.com/
* @copyright Copyright (c) 2008-2012, PageLines [email protected]
*
* @internal last revised January 20, 2012
* @version …
*
* @todo Define version
*/

setup_pagelines_template();

They use a function called setup_pagelines_template to handle this…again, ask theme dev.