How to do spatial adjustment for vector shp files in QGIS?

I have a set of 4 cadastral maps of adjacent locations. I have converted them form DWG to DXF and then to vector shapefiles. They are not geo-referenced/ geo-rectified? I want them to be linked to a co-ordinate system (geo-referenced/ spatial adjustment) so that I can join the four parts together. I also have a shapefile of gps points corresponding to one of the four points.

Can you please tell me how to do this in QGIS or GRASS, not ArcMap?

Thanks, New_QGIS_user