renaming field in BI reporting

Summary

How do I rename a field/column heading in a report?

Content

I have a report that pull a user name and the name of the session instructor.  My data views have user and user.1

When the report exports it labels the username of the user "username" and the username of the instructor "username"

I need to rename the one for the instructor so the report is not confusing.

I attempted to do this in Bi Publisher but A - did not see a way to do it B - had more than 63 fields in the report to do much