If your bank account is attached to your Paypal account, just pay by PP as usual.
If you have either a PP balance or a credit card attached, you may have to inform the seller that you will pay as soon as your bank account is attached and this may take a few days.
Note that because the "e-cheque" takes up to 10 days to clear, using a bank account means the seller will not be shipping until the echeque clears and that paying from a bank account is less secure than paying from a credit card.
