i have process model ,in that i am caleculating sum of two numbers.i published t

Are you trying to call the process within the same Appian system? In that case, use the Sub-Process node to start the process instead of calling it as a web service. A web service will usually return only the process ID.

Here are the main docs on the Sub-Process Activity to get you started: forum.appian.com/.../Sub-Process_Activity

my requirement is through "Call web service" only

Call Web Service is to be used only when the webservice being accessed is outside of the Appian instance. In your case, the process you are trying to invoke is within the same Appian instance. Is there any specific reason why you have been asked to use Call Web Service and not a sub-process node?

Actually,i getting result from the instance which is outside of the appian. so ,i thought that, do we get from the instance with in the appian environment?
Thanks for your clarification

I have something to add here --------------------------

Even if the webservice (wsdl) is outside the Appian and i need the output of the webservice then what will be the steps and approach .

1.Provide WSDL url in the callwebservice node(ex: www.webservicex.com/currencyconvertor.asmx for currency converter).
2.click on "Refresh Services" and provide required data.
3. Go for Data tab, in input you will find a pv in the last. expand that pv and provide values for FromCurrency(ex: "INR" for india) and ToCurrency(ex: USD for US).
4. Go for output tab , save the output value into a pv.