You will need to have registered an account with USPS at http://www.uspsprioritymail.com/et_regcert.html to use this module

USPS expects you to use pounds as weight measure for your products.'); define('MODULE_SHIPPING_USPS_TEXT_OPT_PP', 'Parcel Post'); define('MODULE_SHIPPING_USPS_TEXT_OPT_PM', 'Priority Mail'); define('MODULE_SHIPPING_USPS_TEXT_OPT_EX', 'Express Mail'); define('MODULE_SHIPPING_USPS_TEXT_ERROR', 'Ha ocurrido un error calculando los gastos de envio.
Si aun desea usar USPS para su envio, contacte con el administrador.'); ?>