Hello Mizuki,
nothing could be easier: go to the settings, then to « contact details & preferences », and finally click on « payment of your orders.»
You will simply need to enter your credit card details. We will charge it once your order has passed the 24-hour window (unless you have opted for the Plus or Pro subscription, in which case you can choose to reduce the production time to 12 hours, 6 hours, or 1 hour).
