In Notifications under Settings you can set up the text that appears for clients such as appointment reminders, confirmations, video session invitations, and other custom notifications. There are three tabs: Reminders, Confirmations, Video Sessions. Each section corresponds to the category of notifications you can modify.
To make changes, simply make your modifications in the text box and select Save in the bottom right when finished. Keep in mind that macros will auto fill with the designated information such as the name of a client (_CINIC-NAME_).