how to connect to XML-RPC webservice?

Hi all 
i am new for XML-RPC
i just want to connect to a RPC web service, i am using C#.NET desktop application 
here are the settings i must aply :

POST /RPC2 HTTP/1.0
User-Agent: Frontier/5.1.2 (WinNT)
Host: betty.userland.com
Content-Type: text/xml
Content-length: 181

i am trying to connect but how can i set the URL for my HTTPWEBREQUEST CONTROL and host header?
 



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