HAL9000:
You can open the dwg file as an object and save it into one of your loaded libraries, this will covert the lines to 3D entities (lines) that can be viewed as part of the model. If the elevation comes in laying down, you can either add a RotX 90˚ command to the 3D Script, or if you don't do GDL, view the object from the correct orientation and save as a new object to change its orientation. This object will show in the 3D views and the elevations, but just as 3D lines.
You could also bring the file in and place it on a Worksheet, then Trace & Reference the Worksheet behind the elevation as a guide.
You should add a Signature to your Profile (click the Profile button near the top of this page) with your ArchiCAD version and
operating system (see mine for an example) for more accurate help in this forum.
David