You an add/update credit card information via either the device or Poynt HQ. Cards on file will be charged for 3rd party app, bundle subscriptions, or a la carte Poynt apps.
Updating via device:
Click on the Account icon on the bottom right hand side. Click on the Add New button and enter in credit card details.
Click on Add Credit Card once completed.
Updating via Poynt.net:
Login into Poynt.net and go to Billing section under Marketplace (https://poynt.net/bundled-billing/payment).
Here you can view current cards on file, as well as add new cards and set them to default.