How do I add new people to an existing Conversation?
You can only add new people to an existing Conversation with three or more people involved and if the This is a group conversation... checkbox was selected when the Conversation is first created.
The first two names of Conversation participants will be listed followed by a blue link that says "...other" , with the number of additional recipients. Hover over the "other" link if you want to see who else is included .
Click the Add People... link  to open the Add Recipients dialog box.
Expand Course Roster
Select a Recipient
The "other" link will update the total number of people involved in the conversation . In addition, a new status line will be inserted into the message list notifying participants that someone has been added . You can always add more people again by clicking the Add People button. In this example, Emily and Max were added, bringing the total to 3 additional people in the conversation.
Newly added participants will be able to read and comment on the entire Conversation, even the messages that were posted before they were added.