If you have ordered the RFID tag, it will be sent to you via Posti directly to the given address in your customer account. Printing and deliveries are handled on a weekly basis so in all cases the RFID should arrive within 2 weeks from the order.
While waiting for the RFID to arrive, you can always use the mobile app to start charging. The credentials are sent to you right after the registration. Once the RFID arrives, they are ready-linked to your customer account and ready for use right away.
You can find the receipt of the payment in the App -> Receipts.