That’s only the code for registering the field group. In your category template you need to add code to get the field, the exact code will depend on how the image field is set up and how you want to display it. To get the value of the field would be something like this
$queried_object = get_queried_object();
$term_id = $queried_object->term_id;
$image = get_field('categories_featured_image', 'category_'.$term_id);