When you receive the text message you can normally click on the link to go back to the fuelService app and it automatically enters the registration code.
However in certain situation the link may not work. If the link doesn't work then please remember the code, then open fuelService and enter the code manually.
We would love to know the situations where it doesn't work so we can fix it for future users, so please open a ticket here on the support portal and let us know if you have problems.