Send a standard message for Classes
To send an email to your Class registrants:

Navigate to Collections --> Classes.
Next to the Class title, click Options --> Messages.
If you have more than one class time and wish to send an email only to one specific class time, click Options --> Messages next to the desired class time.

Click the green + Message button and then select Automated.
To send scheduled, auromated message, clickAutomated. Suggested Article: Send an automated message to classes.
Type in the subject line and body of the email.
Choose if you'd also like this message to go out to students or additional parties. To do so, simply click on the icon for the corresponding group.
To learn more about Additional Parties, check out this article. Suggested Article: Additional Parties

Click Send Message.