I hope your head from the grass trimmer is still OK and you have only run out of the cutting wire.If this is the case unscrew the the Hand Nut at the cutting head .when you take out the nut the head comes appart in 2 pices .you will see where and in what direction the wire (it's Plastic) is wound up in it. wind up about half a meter in to it guide the wire trough the guide holes and close the whole thin up again make sure the wire is not to long (fits in side the cutting cage).if your head is gone you might bring it where you purchased it to get fixed (if you havewarrenty) or bring it to some one who fixes stuff like that!
Mirko Fehrmann, August 2009