From the Trainer Dashboard, click on the "Messages" tab to create a group message.
Click on the "New Message" button to create a new message for your Group.
Choose the group you wish to message by selecting them from the drop-down list.
Write a message to your selected Group by clicking the group name in the drop-down list. Then insert a subject and a message, and click the orange "Send Message" button!
Group members can reply back, and trainer will receive individual responses.
Congratulations, you just mass messaged your Group.