On the Patient Home Screen:
Confirmed appointments via SMS are listed in the lower-right under Notes & Contact History.
From the Schedule:
In the lower-right of the Appointment Tile, hover the cursor over the Appointment Note ellipsis(…).
Click the Appointment Tile, and select the Pencil icon to edit.
In the lower-left is an appointment note regarding the SMS confirmation.
Click Reminders for additional information on the SMS message.