If you are wanting to edit your communication templates you will need to access your Settings > Communication > Scroll to the bottom until you see the Templates section.
Within the Templates section of your communication setting, this would be the easiest way for you to edit your communication templates such as your appointment reminder, booking confirmation, etc.
To view the template just click on the Edit button and you will be taken to the template. If you want to know how to create an Email template click here, or if you want to know how to create an SMS Template then click here.
Although it says Text Message and Email just above the template the correct template may not actually be placed below, please ensure the correct template is set.
Please Note: When creating your SMS Template please take into consideration that you cannot add your logo.