How to enable "Web Service Call" option while using import Soap option in Web Service protocol in LR

We have to create LR script using Web Service protocol.

We have WSDL file and know the operation to select, but dont know the arguments to be passed in that client did not give and say dont know abt this.

So we tried to create script using Import Soap option with XML file, but we observed the "Web Service Call" disabled and dont know the reason and how to enable it.

Could any help me on how to enable this option?

Then how to identify the argumentsto be used in the generated script post enabling above option.

PFA is the screen shot of same.

Expecting your reply soon and appreciate for the same.

Thanks

Senthil