Go to Setup and then Provider/Staff

Find the provider name in the list and go to the right on the screen and click the Add/Edit button under the Appt Email

At the top of the screen you have the option to select the template you want to modify - either the email template or SMS template

Next you have the option to set the number of days in advance the reminder should be sent

The next option to set is either Individual or Online.  Individual is for regular in person sessions.  Online is the option for telehealth sessions.