How do you send a group email message
Hi Calvin Hudgins , and 
You can learn how at How do I send a message to a user in a group in Conversations as a student?
This process is the same regardless of user role.
I hope this helps,
Kelley
Hi Calvin,
I will assume you are wanting to message a group in a class and not a stand alone group created on the root or sub-account level. For the course group, it looks like a guide exists to address this issue. However, either I am terrible at following instructions or Canvas made some updates which changed the process. Either way, here is the guiding document How do I send a message to a user in a group in Conversations as an instructor? but I will also jot down the process that worked for me, which is different than the guide:
Open Canvas Inbox
Compose a new message
Select your course
Click on Address Book icon
Select Student Groups filter
Choose Group and select ALL or choose individual or multiple group members