You have to contact the USPS to get your own login id and password in order to access their API. This is the first place to start with that process.
http://www.uspswebtools.com/registration/
Once you fill out the form they will email you something you need to fax back to them. Once they get it they will issue you an id and pw with access to the test server. When you get this email from them just email the right back and say that the test went find and you need production server access. Once you get confirmation from them with the production server info, then you can insert YOUR id and pw into the shipping module of Agora and the USPS API will work for you.
Carol
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Carol aka SouperMom
http://www.soupermom.com