Each card (physical or virtual) is connected to a specific wallet, so to top up the card you basically need to top up the wallet. How to top up a wallet, you can read here, if you are in France and here, if you are in Germany.
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You can connect your card to the wallet in the process of issuing/creating the card.

❗ It is important, that once you have connected the card to the specific wallet, you won’t be able to reconnect it to another one.