USPS Web Tools ???

I tried to search for the USPS Web Tool Integration with Zen cart.
But i was not able to find the things i wanted. May be i am not typing the correct keyword.

Can any Please Help me out!!!! I dont have any knowledge of these Postal shipping services.

If i need to install i will just go to
ADMIN/MODULES->SHIPPING then simply click and install and provide the id(I am not yet registered to provide the id).

But how i need to configure and then how i will be able to make the charges of the USPS apply for Shipping estimate cost?
( [I am thinking that USPS charges will be based on zone to zone shipping or on weight basis.]

[For those if i make changes in the ADMIN/MODULES->ZONE RATE will they be applied to Zonal shiiping estimate. Then for weight if i change ADMIN/MODULES->TABLE RATE will they take effect.]
).

Configuring meant the changes for Zone rate and Table Rate or something else.

I will be very Thankful for your replies or comments.