Web Service with SE37

hi,

I'm creating a Web Service from SE37. After given the name of the Virtual Interface (ZUser), the name of the Web Service Definition (ZUser) and the package ($tmp) the system ask me to enter a REGISTER OBJECT for Object R3TR CLAS /1BCDWB/WSC0........

Why?

Wich object is it?

Do I need to register once?

Thank you for your help

joseph