Not able to add post slider on blog page

I want to add support fot Feature Content (post slider mechanism) for my Site Origin Unwind theme.

I put to function.php

add_theme_support( ‘featured-content’, array(
    ‘filter’     => ‘siteorigin_unwind_get_featured_posts’,
    ‘max_posts’  => 20,
    ‘post_types’ => array( ‘post’, ‘page’ ),
) );

But I dont know where to put this code?:

function mytheme_get_featured_posts() {
    return apply_filters( ‘siteorigin_unwind_get_featured_posts’, array() );
}

when I putting this code on the end of function.php I break whole page.
can you give me some instruction how make this unwind theme work with jetpacj feature content (I read this one https://jetpack.com/support/featured-content/#theme-support)

My page is http://www.konkretnaforma.pl/
Its self hosted page,
I have word press version 4.8.2
Unwind theme version: 1.1.4
Jetpack version 5.4