How to use existing workflow in BPM

Hi

I am trying to use an existing workflow in S/4 as one of the steps of my BPM process in NWDS . But I am not able to find a connect or correlation that I can make .

I have looked at the following link in help.sap.com

Adding a Business Workflow in BPM Process Diagram - Modeling Processes with Process Composer - SAP Library

I am able to import the workflow but not able to use it . Is there any standard document which provides more detail on how to use the workflow in my BPM process.

Thanks

-Alok