To use About Time you need sufficient prepaid credit. You can view the current status of your credit at any time in the app.
You can top up your credit by choosing one of the bundles, 1, 5 or 10 years. The larger the bundle you choose, the lower the amount per month (converted).
To purchase a new prepaid bundle, use the About Time app. Via the menu, click on "Settings" there you can go to "My credit". If you press the "Top up credit" button, you can choose the pre-paid bundle that suits you. These bundles are available for purchase for periods of 1 year, 5 years and 10 years.
Payment for these bundles is made directly via the Google and Apple App Stores.
On this page you can read more about 'My credit'.