You need to know the address of the web service.
In your windows project right click web references in your project explorer window and then click 'add web reference'
You will be provided with a dialogue that asks you to enter the address of the web service.
Provide a name for the web service and you are away.
This creates a proxy in your project that hanbdles all the details of SOAP, but you dont need to worry about that.
In your code you create a new instance of your proxy object by usaing the name you gave the web service when adding the reference.
MyWebService myservice = new MyWebService();
Then you can call any method provided by the service from the newly instanciated object myservice.
They say, best men are molded out of faults,
And, for the most, become much more the better
For being a little bad.