The USPS settings can be accessed from the Settings panel, which is at the far right of the main menu.
Quick Note: Your USPS settings may need to be enabled first. This can be done by contacting our live chat support.
I will now go top-to-bottom and cover all the fields in the USPS Settings.
The first area that you will is the top-up window. You will see your credits total here and will be able to top-up using your credit card.
Before topping up a pop-up window will appear reminding you that this will charged from your default card that you added in your subscription settings.
Below, you will see your Account Information, which you can adjust. You can set up an auto-renewal feature where it would top up your USPS account after reaching the set threshold, you can do that by entering the desired amount and marking the "Auto Renew Enabled" checkbox.
You are also able to edit the Credit Card information by clicking on the checkbox "Edit Credit Card Information", which will allow you to enter the new payment method