The U.S. Department of State explains the Hague Adoption Convention at Understanding the Hague Convention Page. The long and the short of it is that intercountry adoptions amoung Hague Convention Countries are heavily regulated by both the U.S. (which is a Hague Convention Country) and the other Hague Convention Country. One of the requirements is that you will need to work with an agency that is an accredited adoption agency if you wish to adopt children from a Hague Convention Country. The above web page has both a list of accredited adoption agencies for each state and a list of Hague Convention Countries.
Please note that there are several exceptions that may exclude your adoption from the rigors of the Hague Convention. Before seeking out an accredited adoption agency, I would advise you to consult with an attorney well versed in both adoption and immigration law to determine if the child you wish to adopt is excepted from the Hague Adoption Convention.
The attorneys at Steffas and Associates, P.C. understand well the junction between adoption law and immigration law. They are well able to give you guidance concerning the Hague Adoption Convention and it exceptions. Ms. Steffas and her associates may be contacted at www.SteffasLaw.com.