You'll have to find all of the play money hands in the "Hands" table. Best way to do that is to change the date filter to the time period the hands came from, switch the view to Files, and choose one of the files for the play money hands. Next, you need to select all of the play money hands (you can multi-select several hands at once), right-click the Hands table and select Delete Hand(s). Let me know if any of this isn't clear.
Thanks,
-red