Sub categories in categorised bibliography

I am using EndNote X7. I want to get sub categories in the bibliography like:

Primary Sources

            Archival Sources 1

            Archival Sources 2

Secondary Sources

            Journal Articles



–I have tried going through edit output style > Bibliography > Categories and adding them there. It appears to gererate a kind of list which I want. However I am facing a problem. If I want Manuscript A to come under Archival Sources 1 and Manuscript B to come under Archival Sources 2, how would I be able to do that? Thanks.