How does one hook up with the USPS shipping options so when someone orders, shipping is calculated based on weight by USPS rules? I don't understand what I need to do in the admin section to make this happen. I want to use First Class Mail to 13 oz then switch to Priority Mail for over 13 oz (which requires use of zones for calculating cost).Thank you!
I do not think that you can set the shipping method. You use the USPS shipping API to determine the available methods and cost. You provide the weights in your product setup. You need to request credentials to set it up here http://www.uspswebtools.com/registration/
