1. To begin with , click on "Stores" and choose the store you want to add the credit card for. Hit "Manage" to continue. 
2. From menu bar, click "Settings" and then "Add new Credit Card".
3. In the pop up window, insert the credit card details and click "Add card" to save it. 
4. Once the credit card details are in place, please click "Continue" and insert your VAT number (optional). For more information about what is a VAT number please refer to following link: https://picanova-api.freshdesk.com/support/solutions/articles/77000507932-what-is-a-vat-identification-number-vatid-
5. After having the VAT number (optional) in place, click "Save". The "Sandbox" button in going to automatically turn into "Live" mode now.
Please note:
If your credit card is declined, this may occur if your credit card has not yet been registered for online legitimation. In this case, please contact your credit card provider.