Steps to add child datasource into custom entity DMF/DIXF

What steps to do to add a child datasource field to a custom entity.
1.I have added datasource in dmfxxxquery and provided a relation
2.I did the mapping from source to staging, staging to target.
But still I dont see a record insert in childdatasource?
if i try to insert using code in insertUpdate method its working fine. (I did this to see if i am getting value from source to entity or not. Yes I am getting that.)
Did i miss any steps ?