Adding item field to a journal entry

In my prior job we had multiple revenue systems (13 of them). Only 2 directly interfaced with NetSuite, either directly or indirectly through a connector. We used a journal entry to upload billing and revenue recognition through a journal entry. The upload included the item field and some associated custom fields as well as the customer field. If I pulled a saved search on revenue the item field was populated with the information from the JE just like it was from the 2 systems that interfaced with NetSuite.

Now I am with a new company implementing NetSuite. We are trying to upload our history through JEs so NetSuite does try to do revenue recognition on them. Unfortunately, I can't find how to add these fields to the JE form.