Carefully remove the back by unscrewing it (you can use a pair of long-nose pliers if they have sharp enough jaws.) On the movement near the stem you will find a very small screw head. Turn the screw head counterclockwise until it stops. If a screw starts to come out, it isn't the right one. You should then be able to gently insert the stem until it seats with the crown against the bezel of the watch. Now turn the screw head clockwise until it stops. The stem should be reinserted and you should be able to wind and set the watch normally.
JimH
August 2010