Bro,
Its simple I request you to follow below steps :
a) Create 1 char domain
b) And add field in below structures assigning assigning domain which you have created.
INCL_EEW_PD_HEADER_CSF_SC
INCL_EEW_PD_HEADER_CSF
c) Check field create in BBP_DOC_CHECK_BADI
Thanks
Ankit