"Não existe falhas, apenas resultados e feedbacks"
Once you've subscribed your user, you'd send their subscription to your server to store in a database so that when you want to send a message you can lookup the subscription and send a message to it.
To simplify things for this code lab copy the following details into the Push Companion Site and it'll send a push message for you, using the application server keys on the site - so make sure they match.