How to Hide the "Posts Footer Manager" Admin Menu

function plt_hide_intelly_posts_footer_manager_menus() {
	//Hide the "Settings → Posts Footer Manager" menu.
	remove_submenu_page('options-general.php', 'intelly-posts-footer-manager');
}

add_action('admin_menu', 'plt_hide_intelly_posts_footer_manager_menus', 11);

Where do I put this code?