If you have created a self-sign-up group within your course, you can message students who have not yet signed up for a group and remind them to do so.
In Course Navigation, click the People link.
Open Group Set
Click the View User Groups button  or an existing group set .
Confirm Group Creation and Options
Open the Settings of the Group  and then select to Edit  the Group.
Verify that the box is checked to Allow self sign-up .
If you changed any options while here, be sure to click the Save button  so that the changes will take effect.
Message All Unassigned Students
To send a reminder to students who have not signed up for a group, click the Group Set Settings icon , then click the Message All Unassigned Students link .
Message Students for Self-sign-up
Type your message into the text area . If you wish to go back, click the Cancel button . When you are finished with your message, click the Send button  to message students who have not signed up for this self-sign-up group.