Hey Guys,
A good place to start is the FAA site
http://registry.faa.gov/airmen.asp Go to the details on Verification of Authenticity of Foreign License, Rating, and Medical Certification. You will find your initial application form there plus an FAQ list.
This is all about getting your initial FAA US Private License based on your foreign license which is straight forward, but suggest you contact appropriate Flight Schools for best details on continuing up to convert your ATP, which will require a flight test. There is more than enough info at the above site plus its links to get you going a long way. Good Luck.
FF
P.S. Getting an FAA IR based on your foeign IR is also very straight forward, its just a computer test having read the prep book which you can buy at most FBOs.