Note:  You must be the Group Owner to do this. From the Group Manager Feature the Group Owner sends invites to the members to become part of that specific Group and can choose to give permissions to other users.  

Sending the invitation
1. Enter the username in the text box that you want to invite
2. Select the dropdown box of roles and choose the “HR Admin” Role
3. Click Send invite

The Member will then have access to the training register