To register a card, you must set the allowCardStorage field to TRUE when calling Creates a payment session. .
This will result in the customer being offered to save their card on the payment page :
To force the registration of the card (i.e. the client will not have the choice), you must set the value TRUE in the field forceCardStorage.
Recover the id and label of the registered card
In return for the payment, this information is returned in StoredCardID and StoredCardLabel.