How to Hide WP-Invoice Admin Menus

function plt_hide_wp_invoice_menus() {
	//Hide "WP-Invoice".
	remove_menu_page('wpi_main');
	//Hide "WP-Invoice → View All".
	remove_submenu_page('wpi_main', 'wpi_main');
	//Hide "WP-Invoice → Add New".
	remove_submenu_page('wpi_main', 'wpi_page_manage_invoice');
	//Hide "WP-Invoice → Reports".
	remove_submenu_page('wpi_main', 'wpi_page_reports');
	//Hide "WP-Invoice → Settings".
	remove_submenu_page('wpi_main', 'wpi_page_settings');
	//Hide "WP-Invoice → Add-ons".
	remove_submenu_page('wpi_main', 'wp-invoice/wp-invoice_add-ons');
}

add_action('admin_menu', 'plt_hide_wp_invoice_menus', 1000);

Where do I put this code?