How to Hide Pivot QR Admin Menus

function plt_hide_pivot_qr_menus() {
	//Hide the "Pivot QR" menu.
	remove_menu_page('pivot-qr');
	//Hide the "Pivot QR → Links" menu.
	remove_submenu_page('pivot-qr', 'pivot-qr');
	//Hide the "Pivot QR → Settings" menu.
	remove_submenu_page('pivot-qr', 'pivot-qr-settings');
}

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

Where do I put this code?