The way BeehiveOnline works is that the group is the basic component of the system. You can only see participants that share a group with you.
So in your situation it looks like the user is not inas a shared group so you have to add the users to a group first and then they will show in the system as being available to add to Workspaces. If this is the default Workspace they will be automatically added to it as they are provisioned into the system.
The process is the same for Oracle and non-Oracle users - they are all the same to the system