SQL server is probably not the target platform you want to use for this; is this supposed to send / retrieve information from the web service and return it to a user, or just blindly send to your web service?
anyway, to do it via SQL server,you will have to create and use a CLR(Common Language Runtime) procedure which is specifically designed to call your web service with the appropriate parameters, and consume any answers back.
there's lots of examples out there, does this help?
https://www.google.com/search?q=SQL+CLR+to+call+a+web+service&oq=SQL+CLR+to+call+a+web+service
Lowell