To create custom emails to send to customer to provide notification then the Email Template option is where you achieve this. You can click on Settings in left navigation bar and then click on Email Template.
You can customize the following emails:-
- Welcome Email
- Appointment Accept Email
- Appointment Reject Email
- Appointment Start Email
- Appointment Complete Email
- Invoice Create Email
- Invoice Reminder Email
To create custom email for new customers, select the email and then click on the 
The header is where the information will go right under the customer name.
The body will be the standard text DoTimely uses for the email.
The footer will go under the text DoTimely substitutes for that email.
You have option to add both header and footer, only one of them or leave them black to send the standard DoTimely email.
When you have made your changes just click save to save them.
Select the email you have changed and then you can send yourself a test email by clicking