How I could add a new label in post page

Hello,

I was wondering how I could do like on the picture. Because I have looked at the code and am not sure about how to do that.

Because page are generaly declared like this if I m right but don t what I m allowed to do to make my modification :

$labels = array(

'name' => __( '', '', ),

'singular_name' => __( '', ),

'search_items' => __( '', ),

'all_items' => __( '', ),

'parent_item' => __( '', ),

'edit_item' => __( '', ),

'update_item' => __( '', ),

'add_new_item' => __( '', ),

'menu_name' => __( '', )

);