Need help with Table and join details for Datetime and User details for PO, REQ, INV Approval.

Need help with Table and join details for Datetime and User details for PO, REQ, INV Approval.

I have the below draft query but its tough to join these with PO, REQ, INV tables

select

S."THREAD ID"

,S."STEP INSTANCE"

,S."PROCESS ID"

,S."DEFINITION ID"

,U."USER"

,U."STEP STATUS"

,U.DATETIME

,W."EVENT NAME"

from EOAW_STEPINST S

INNER JOIN EOAW_USERINST U

ON S."STEP INSTANCE" = U."STEP INSTANCE"

INNER JOIN EOAW_WL W

on S."THREAD ID" = W."THREAD ID"

I have below table details but not clear on the joins:

PYMNT_VCHR_XREF

REQ_PO_INQ_VW