Trying to set up USPS shipping.

I and on http://www.usps.com/webtools/ and see the following
Address Information API
Deliver Information API
Rate Calculaters API
Shipping Label API
Carrier Pickup API

I have my userid and password but am not sure which one of these
API's to use.

Can someone tell me.
Thanks

Howard

I added a reply to this at this link

https://www.nopcommerce.com/Boards/Topic.aspx?TopicID=1742#8551

I was not sure if the general / development was the appropriate place.