Hi myshabbichic,
In order to configure your shipping profile to offer flat rate shipping to the United States and use the "Contact Seller or See Item Description" option for international shipping, you will first want to check the bubble next to "Flat Rate Shipping" and check the boxes corresponding to the countries/continents to which you are willing to ship in the section above.
In the "Domestic Shipping Services" section, select the shipping service(s) you would like to offer from the appropriate pull-down menus and enter your flat rate shipping costs for each service in the adjacent "Cost" fields. Then, simply leave the "International Shipping Options" section alone and, when you post the listing, it will reflect the "Contact Seller or See Item Description" option with respect to international shipping.
Any additional questions or concerns? Please contact our customer support department using the appropriate link on our help page: http://www.auctiva.com/free-auction-software-help/help.aspx
-Mike