In K2 Studio you can add a web service reference to your process by clicking on the References Icon on the Home Tab.  Once the web reference has been added you can invoke a web service call in you process by using the reference event wizard.

I hope this helps.

-Eric

Good one but K2 is generating a DLL reference where URL is hardcode and even DLL is copied at statis location ..... How to change this if we decided to move to production later :)