When creating a WebServiceDesriptor you can choose if it is meant to be a provider (hosted by you) or a consumer (calling the WebService somewhere else).
In your case you are looking for a consumer. You can specify from where the Descriptor should be created and you can give the URL of the external WSDL as a parameter here.
For IS this would look like:
http://:/ws//?WSDL
Regards,
Holger
#Integration-Server-and-ESB#webMethods