If you look at the passenger side you will see clip that the wiper arm slids onto. You need to copy it on the drivers side. If it is just the wiper then this will work only if you have all the bits with it. If the whole arm has come of then you will most prob need to replace the nut that holds it onto the wiper motor. If you find this still to hold you can take it to Halfords and they will fit it for a couple of quid.
Dean, January 2010