Shipping for beginner using USPS

I'm sorry I am a beginner and I have some questions about shipping & USPS:

1. I want to offer a free shipping in USA and $7 shipping cost for international . I do not want to send to Africa& Brazil but other then this two place I want to ship be able to ship anywhere else . How do i do that?

2. I just registered to USPS Web Tool and I got my user name a password. What I'm supposed to do next?

Thank you very much for your help.

a little confused.
Sounds like you want to do "Zones"
Admin->Modules->Shipping->Zone Rates
in the first zone put just US and then in table enter :0 ( for all, and 0 for shipping price)
in the 2nd zone put all the other countries and then in the table enter *:7.00

USPS Web Tools is needed for calculating rates based on USPS rates

2. http://www.zen-cart.com/content.php?284-how-do-i-set-up-the-usps-shipping-module

Thank you I've done it but still every time i add something to my cart it double the price.
I just sent you a private message with my website.

In Zone Rate zone there is no setting for:
*:0.00
*.7.00

Try using:
Skip Countries:
(Enter the 2 character ISO codes for Countries that you do not ship to)

Zone 1 ...
US
10000.00:0.00

Zone 2 ...
00
10000.00:7.00

NOTE: USPS is getting real time quotes based on weight and usually is not used at the same time as Zone Rate zone ...