Moodle currently does not have an internal email function associated with your course.
To send an email to your entire class you will have to use your University of Lethbridge email account.
The mailing list associated with your course is as follows:
Your course name, number, and section, followed by @uleth.ca
An example for ANTH 1000 A will look like this:
By using your class mailing list you will address your entire class and all students will receive the email message.
If you prefer not to email your class via your UofL email account you can alternatively use the forum tool in Moodle. With this option all students will be able to read and reply to all messages within the class. They will see each others postings as well.