How to Hide Newspack Newsletters Admin Menus

function plt_hide_newspack_newsletters_menus() {
	//Hide "Newsletters".
	remove_menu_page('edit.php?post_type=newspack_nl_cpt');
	//Hide "Newsletters → All Newsletters".
	remove_submenu_page('edit.php?post_type=newspack_nl_cpt', 'edit.php?post_type=newspack_nl_cpt');
	//Hide "Newsletters → Add New Newsletter".
	remove_submenu_page('edit.php?post_type=newspack_nl_cpt', 'post-new.php?post_type=newspack_nl_cpt');
	//Hide "Newsletters → Ads".
	remove_submenu_page('edit.php?post_type=newspack_nl_cpt', 'edit.php?post_type=newspack_nl_ads_cpt');
	//Hide "Newsletters → Categories".
	remove_submenu_page('edit.php?post_type=newspack_nl_cpt', 'edit-tags.php?taxonomy=category&post_type=newspack_nl_cpt');
	//Hide "Newsletters → Tags".
	remove_submenu_page('edit.php?post_type=newspack_nl_cpt', 'edit-tags.php?taxonomy=post_tag&post_type=newspack_nl_cpt');
	//Hide "Newsletters → Advertisers".
	remove_submenu_page('edit.php?post_type=newspack_nl_cpt', 'edit-tags.php?taxonomy=newspack_nl_advertiser&post_type=newspack_nl_cpt');
	//Hide "Newsletters → Settings".
	remove_submenu_page('edit.php?post_type=newspack_nl_cpt', 'newspack-newsletters-settings-admin');
	//Hide "Newsletters → Tracking".
	remove_submenu_page('edit.php?post_type=newspack_nl_cpt', 'newspack-newsletters-tracking');
}

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

Where do I put this code?