How to Hide iTech Doc Admin Menus

function plt_hide_itech_doc_menus() {
	//Hide "iTech Docs".
	remove_menu_page('edit.php?post_type=doc');
	//Hide "iTech Docs → iTech Docs".
	remove_submenu_page('edit.php?post_type=doc', 'edit.php?post_type=doc');
	//Hide "iTech Docs → Add Page".
	remove_submenu_page('edit.php?post_type=doc', 'post-new.php?post_type=doc');
	//Hide "iTech Docs → Categories".
	remove_submenu_page('edit.php?post_type=doc', 'edit-tags.php?taxonomy=catrgory&post_type=doc');
}

add_action('admin_menu', 'plt_hide_itech_doc_menus', 15);
Where do I put this code?