How should I add a data item to a report?

Hi,

I need to add a data item to a version of a report in RDA so that I can add the item to a BI Publisher report.

This is what I tried:

I found the data item in Business View Browser and dragged it onto the report. Then in event rules I added the item to an existing if statement - this statement contains related report variables. When I use "assignment/expression" I can only add a report constant (RC) for the data item. This will work and present the data I need on the report but I'm not sure if this is the best way to add the variable.