From your Client Portal, click either "Unpaid Invoices" or the "View All" button in the Unpaid Invoices box:
In the My Invoices section, you'll see any outstanding invoices on your account. Note that invoices are generated 14 days prior to their due date. Servers whose invoices are not paid by their due date may be subject to termination.
In the Mass Payment area, you will see all outstanding invoices in which you are able to pay
Select your desired payment method. For this tutorial, we'll be paying with Bitcoin.
Once selected, click Pay Now and you'll be taken to payment processing where you will be given an amount of BTC to send and an address you need to send those coins to.
Once paid, you're all set!