Hi
A couple of pointers when importing DXF files into Alibre. Experience from years of frustrating imports.
1: Save original DXF file as a copy suffix "Alibre import."
2: Open Copy in 2D software and delete any layers with items not required for import .
3: Go through remaining drawing items and explode any Blocks.
4: After exploding blocks go through drawing and delete any overlaping (Double) lines . Multiple overlapping lines play havoc with constraints later in Alibre.
5: Depending on what you are drawing I save a single file showing a Plan, Top and side view of the imported drawing. ( Have a common datum point in each view)
6: Import into a blank Alibre drawing.
7: Open New Part
8: Create new sketch on each plane . Cut and past require view from Alibre Drawing ( use Common Datum point create in DXF drawing)
9: At this point it depends on What you are planning to design. I often just Lock the Sketch ( Constraint Lock feature)
10: Create a new working sketch and use "Project to Sketch import tool" to grab required lines from DXF control Sketch. ( Highlight maintain association tick box)
Hope this helps
Pete