Use the Texting component from the Social group of components.
Here is an example that you can modify to your need:
There is a button, ButtonSMS that, when clicked, will cause the SMS to be sent. Then, you need a phonenumber. In this example it is in LabelNummer.Text and the message you want to send in TextBoxMsg.Text. You set these as phonenumber and message in the Texting componenet and then you call Texting1.SendMessage, and off your SMS will go!