Help With SOAP UI -- Parametrization

Hi ,
      For Load Testing I usually use HP Load Runner 9.0 ..
      In that ..if we want to execute our script sequentially for different users or phone numbers ..
and to declare it we have to:

                1. select string, to be replaced with a parameter
                2. right-click on the selected text
                3. 'Replace with a parameter'
------------------------------------------------------

  But in Soap Ui .. I am unable to find out how can I replace the input phone numbers .. Do we Groovy script for that .. SOap UI PRO .. ?? I am using Soap Ui 3.0.1 .. If possible please let me know the steps ..thanks


Surya