It depends on the reports in question, but the easiest way to customize reports (with minimal customizeability)... Edit the report. If the edit button is disabled, just save-as to a new report. Any available fields in the box on the left can be moved to the box on the right.
That only takes a few minutes, so if the fields are all available then you're good to go. If not, that's when you need to dig into the report definition customizing which is a bit more time consuming.
