Adjustment Register - Rxi Report

The adjustment register is an Rxi Report.  Rxi reports gives the flexibility to add and drop columns and the layout using Report Xchange Designer.  We want to add two new columns - Comments and Adjustment Reason codes. 

Can some one help us how we can add additional columns to existing Rxi Report (columns which are not seeded as part of the original report)

Any feedback from the community will be greatly appreciated.