A benefit to loading a balance on your account is that any future invoices will be paid automatically from this so you do not need to worry about having servers suddenly shut down due to non-payment.
Here's how to do it!
From the Client Portal area of your account, Click Billing and then Add Funds
Select your preferred payment method and enter how much you would like to load your account with and click "Add Funds"
If you chose Bitcoin as your payment option, you will be taken to a payment processing screen where it will provide the amount of coin required and the address it needs to be sent to.
If you chose CC/Debit Card as your payment method, you'll see the following. It is important to note that your name and billing details do need to be accurate or else the payment will not process properly.
You're all done! Now you will no longer need to pay attention to invoice due dates. All you'll need to do is top up your account balance from time to time and billing will be taken care of automatically for you!