In the Solution Explorer, right click on References and select Add Service Reference.
Paste the WSDL URL, press Go, use Velocity as a Namespace (to make it easier to follow the code examples) and press OK. If you expand VelocityService in the Services box and select VelocityPort, you will see all of the available functions listed on the right.
Use the Velocity namespace in your code:
using ConsoleApplication1.Velocity;
Create a VelocityPortClient object. All of the Watson Explorer Engine API functions will be available as methods of this object.
VelocityPortClient port = new VelocityPortClient();
QuerySearch qs = new QuerySearch();
port.QuerySearch(qs);