[Theme Horse Support Team]

Hi Eva,
We also have not implemented it still in our theme. The file is inside the interface folder -> inc -> structure -> header-extension.php

You need to identify the code and just create the child along with functions.php file and first unhook the functions and the edit the code.

http://codex.wordpress.org/Child_Themes

IF you will be unable to fix it then you need to hire a developer to fix the issue.

Thank you!