Navigate to the report page, then select Scheduled or Not Scheduled, then click the name of the report where you'd like to modify the send options.

This will open the report editor. At the top, click Schedule to open the scheduling settings.

This will open the schedule page, which has two distinct parts. The top section is for editing the Schedule of the report.

Scroll down to see the Email section, where you can make edits to the recipients, subject, and message that are sent with the report.

Make your desired changes, then click "Save".