Featured image on product theme

Hello,

I am tring to add a featured image. This theme does not seem to have that feature even though the important wordpress xml shows it on the older post.

I can not add new ones in this theme.

I created a child theme and added the follow code to the functions.php.. (which was black btyw except the opening and closing php tags.

// Add support for Featured Images
if (function_exists('add_theme_support')) {
    add_theme_support('post-thumbnails');
    add_image_size('index-categories', 150, 150, true);
    add_image_size('page-single', 350, 350, true);
}

But it does not work. Suggestions ?