First, Crystal will not generate any data that is not already in your data source (generally speaking, there are tricky exceptions).  Are your comments already in the data source?  In that case, it's a fairly simple matter of adding the comments field to the data selection, and from there to the report.

If your comments are not in the data source then, speaking hypothetically, how do you envision them being entered in the report?  Keep in mind that Crystal is not interactive.  With the exception of activating drill-downs, once the report is generated, it is as static as a piece of paper.  (This is extremely intentional, as it is often generated to a piece of paper.)