How to set up USPS shipping calculator?

Using Opencart 3. I installed and enabled the USPS shipping extension, did what I could in the configuration panel for it and enabled it. Now on a customer cart when I click 'get quotes' in the 'estimate shipping and taxes' dropdown I get a popup with an error message;
'Authorization failure. Perhaps username and/or password is incorrect.'

I assume opencart is trying to log on to my USPS account and get an estimate. I am seeing where to enter my user ID and zipcode in the configuration panel for the extension, but no password field. What should I do?

You don't need a password, so most likely you're using the wrong account information. The account you want to use is a "USPS Web Tools" account ID. You can sign up for one free here:

https://registration.shippingapis.com

If you're not sure if that's the account you're using, try signing up for a new one, and it should work correctly after that.

That worked, thanks very much for the suggestion.