Just follow the steps on myTTNC to add SMS credits to your account:

1. Log in by either clicking on the login button in the header or by going to www.myttnc.co.uk
2. Click on the Top Up tab in the left hand menu.
3. Click on the Top Up button in the SMS Balance row.
4. Select the amount of SMS credits you want from the drop down box.

5.Click the Add to basket button.

6. Proceed through the order process to make payment and add SMS credits to your your account.