I remember there is a topic about this here, but anyway just download the .lwa's from lightworks-user site (not all materials listed there works with ArchiCAD). Copy the files (.lwa's) to :
..\graphisoft\ArchiCAD 9\Add-Ons\Visualisation\smdata\archives
In this way you do not need to specify location as they are in default location of ArchiCAD
Mbarouk