Add widget area above slider on Mantra presentation page

Hi, I think this has been asked before but I can’t find a positive answer. I have Mantra doing almost everything I want – except I need a widget area below the header on the presentation page.

I’ve learned how to set up a child theme, I have the new widget area registered and ‘live’, and I have the code to add the widget area – but I really don’t know where to place it – i.e. in which file. My code (copied from somebody modding a different theme) is:

// Place the widget area after the header
add_action (‘__after_header’, ‘add_my_widget_area’, 10);
function add_my_widget_area() {
if (function_exists(‘dynamic_sidebar’)) {
dynamic_sidebar(‘Extra Header Widget Area’);
}
}

This one thing is all I need before going live with my website, so I’d be very grateful for help or ideas.

Thank you.