You can pay a due invoice directly within your account.
Pay Your Invoice
If you have an invoice due in your account, you will automatically be directed to the Billing section of your account to process the payment.
If you don't see that, you can hover over your name in the top right corner of your account. From the drop-down menu that appears, you will want to click on My Account.
From the left hand side of the page, click Billing.
On the Billing page, scroll down until you see a section labeled Invoices. Next to the invoice that is due, click the Pay Now button.
Enter the credit card details that you want to use to pay invoices moving forward.
Once you are done, click "Pay Now" - the amount due will be charged to your credit card.