How to integrate mvaayoo messaging API code in C# windows application

Hello,

Want to send sms using this below API but don't know where I have to write this code on formload or on button click?

string strUrl =  "http://api.mVaayoo.com/mvaayooapi/MessageCompose?user=password@gmail.com:yoo@1234&senderID=TEST SMS&receipientno=919993154778&msgtxt=This is a test from mVaayoo API&state=4";
WebRequest request = HttpWebRequest.Create(strUrl);
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
Stream s = (Stream)response.GetResponseStream();
StreamReader readStream = new StreamReader( s );
string dataString = readStream.ReadToEnd();
response.Close();
s.Close();
readStream.Close();

And I am using this below controls