Hello Abishek,
As per the note, it says to create the implementation for the Badi BBP_PO_INBOUND_BADI, and code for implementation is also given. Just create the implementation for the Badi and it solves the issue.
Steps in Creating Badi implementation:
1. Goto t-code SE18, Select Badi and give Badi name (In this case it's BBP_PO_INBOUND_BADI)
2. Goto Enhancement Implementation -> Create to create Implementation for the badi (Menu Bar)
3. Specify the Implementation name, It's the class name in which you have to past the code given in the OSS note.
4. Save the implementation and a class will created, where the code needs to be pasted.
Double click in the method BBP_MAP_BEFORE_BAPI, after creating Badi implementation , give the custom code.
Please refer documentation of Badi and its implementation for further details.
Hope it helps !!!
Regards,
Deepan Swaminathan.