USPS Shipping

 USPS Shipping  - USER ID #

You can't use the same login username for your API ID#.
You need to register for the API separately.  

Once you register, USPS will give you your User ID # which you then enter into Income Activator platform to calculate your USPS shipping costs for your store.

To do that, login to your editor, click on the Top Bar entitled  Store, from the drop down menu select Payment Options, scroll down until you get to the USPS section, and enter in your ID #.

Then go to your online store and do a test to ensure your shipping calculations are correct.