To delete a report, click Recent Report from the menu in the header to view your list of previously run reports.  

Towards the top right, in the Recent Reports section, click the Edit reports button.

You will then see a remove report option shown for each report, and an option at the top to remove all reports.  Select Remove report for each report you wish to delete.

This will remove the report from your list of previously run reports. Please keep in mind, once you delete a report, it is not possible to "un-do" the deletion.  You would need to re-run the search, in order to view the report again.

Please note - if you attempt to delete a report you are currently monitoring, you will be notified that you are trying to delete a monitored report, and will no longer receive updates for that report.