What should be the domain name in google api AppsService..

Question

using Google.GData.Apps;

AppsService service = new AppsService(domain, userName, password);

I am using google APi and i came across a Class AppsService which have parameters domain,username and password..Since i am working locally my domain name is "localhost" and password and username is empty ...Am i right with this or am i making a mistake.Bcoz it gives and 401 erros ,every-time i try to use those ....the error comes when iu se it here "service.RetrieveUser("username")"

plz help