Okay very quickly ....
Go to - FILE > IMPORT/EXPORT > IMPORT > DWG/DXF (Import) - and import the downloaded DWG file into a new Softplan drawing.
Once imported you need to copy the shapes a number of times depending on the shapes - this one is 8 - It will become clear - Maybe make it 9 and keep a spare - JUST IN CASE.
Once you have the copies, you have to isolate each individual segment, by deleting unwanted lines.
Once they are isolated, go to EDIT > BLOCK FORM POLYGON(S) and draw a block round each portion (I do each one individually, but I believe that you can do them all together - don't know what (if anything) the downside would be).
Once they are polygons go to EDIT > FORM SOLID POLYGON and click on each one. RIGHT CLICK to end.
You should now have 9 solid polygons.
NOTE: Sometimes depending on how the lines join, the polygons will not create correctly. You may have to redraw lines and arcs etc. to suit. Keep trying until it works.
You now have to give them a height. As the total height we need is 4½", I started at ½" and increased each one by ½", so getting the last one at 4½"
Then you have to reassemble the shape by dragging the shapes on top of each other.
The 3D model will now look like this:
Once the 3D model looks right, then in the 3D model go to FILE > EXPORT > DWG, and save the model - it needs to be reoriented, which you can't do in the model.
Now open the SYSTEM LIBRARY > SYMBOLS > WIZARD, and open the dwg model that you just created, and reorient and save as a Softplan Symbol. This will also Generate a plan view, so that it can be used anywhere.
I'm assuming you know how to use the symbol wizard. If not see this thread.