If you have money in your wallet, then you do not need to take any further action - your credit will be used automatically on your next purchase and displayed in the final payment amount.
If the total amount to pay is less or equal to that of your wallet, you do not have anything more to do than confirm the purchase. Your wallet will update automatically in your account and list the transaction.
If there is still an amount to pay, you need to select your payment provider and click on "buy item now".
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