Adding Media To An Appointment Reminder SMS
Head to Account Settings -> Appointment Types. From there, use the dropdown menu next to the appointment type you would like to edit and select "Notifications".
NOTE: Media can only be added to Client Facing SMS Reminders.
Click the "Edit SMS" button to open up the popup for the reminder that you'd like to add media to.
That will open up a pop-up which will allow you add media.
IMPORTANT: Remember to save your notifications after you're finished!