Hi can anyone help please
have on different machines installed elementary OS but unfortunately on this one it doesn't work and cant find a Workspace manager
In Luna, workspaces are only accessible with a keyboard shortcut Super+S or by setting up hot corners. The multitasking view (and its shortcut) was added in Freya.
As an aside, Luna (0.2.x) no longer receives updates from elementary. You should upgrade to the latest release (0.3.2) to continue receiving updates from elementary.