How to Hide the "Image Sphere" Admin Menu

function plt_hide_bt2image_sphere_menus() {
	//Hide the "Settings → Image Sphere" menu.
	remove_submenu_page('options-general.php', 'bt2image-sphere/bt2-imagesphere.php');
}

add_action('admin_menu', 'plt_hide_bt2image_sphere_menus', 11);

Where do I put this code?