B1if Call Service Layer Script Example To Add A UDO Entry

I am new to the the service layer using B1if. I need to populate a UDO using the service layer using the Call Service Layer Script. After looking at the documentation, I really do not understand how to configure the predecessor transformation atom(s). I know how to complete this using a tool like Postman. Hopefully someone can point me in the right direction.

Regards,

Tom Arnold