First, in my opinion, it would be far quicker to completely redraw it in PartDesign.
Having said that, it was easy enough to get it done this way - basically, clipping the file to 1/4 and using symmetry, as follows:
In PartDesign workbench:
Create a New ‘Part’
Add a Body to the Part.
Import your .DXF
Box Select 1/2 of the dxf lines, Delete them.
Box Select 1/2 of the remaining lines, Delete them.
* Now, you have 1/4 the of the shape *
In Draft Workbench:
Select the remaining lines, Convert Bi-Directionally to sketch.
Delete all the Shape lines from dxf (but, keep the new sketch lines).
Move the sketch lines into the Body (created above).
In Sketcher workbench:
Select all the sketch lines
Sketch>Merge sketches (in menubar)
Delete all the sketches of the lines but keep the new merged sketch.
Clip the lines that extend past the H & H axis and close them with a new short line.
* Now you have one sketch of 1/4 of the shape *
In PartDesign workbench:
Drag the new sketch into the Body label
Validate the new sketch (Find and Fix - will delete what’s no longer needed)
Now you have two options
1 - extrude and mirror the extrusions
2 - mirror the sketches and extrude as one unit.
I choose to mirror the Sketches as is more useful/friendly for this particular part)
Mirror as needed to get the final shape (of four quarters)
Now, extrude (Pad) it…
Bingo!
[EDIT] Why did I choose the use 1/4 and Symmetry? Because, so many lines take too long for regeneration/update and I don't like waiting
