I can't tell from the picture, but I think you may have a normal freewheel hub without any provision for a lockring. Round here folks like to call that a suicide hub. It's very dramatic . If that's the case you can either try to fix that thing on there in one of the many ways discussed on this forum in the past (search "suicide hub") or just thread on a freewheel.

If it is a track hub with reverse threaded lockring threads, just get a lockring and put it on there nice and tight. Since Zuess priamrily made campy knockoff parts you'll probably need a campy threaded lockring. Phil, and EAI both make them in that threading.