Conceptual Mass Pick Line/Point of 3D Spline

[tykN3JLE]

Good day
I'm trying to create a sweep extrusion of a spline and it seems that conceptual mass family is the way to go.

However, when I import the DWG into the family, I am unable to select points on the line in order to later spline the points and create Form.

If I were to explode the DWG in Revit, the drawing instead becomes flatten and no longer retains it's 3D-ness.
I've tried PEDIT in AutoCAD to turn it into 3D polyline, but still couldn't pick the points on the spline.

Can someone guide me to the right steps?
The attached files are just the type of edits I've done in AutoCAD to make it work, but to no avail.

Thank you very much !

[tykN3JLE]

Bump 

[ToanDN]

Create a mass and import the spline in. Create another mass and place points on face then place on the spline of the first mass.

[tykN3JLE]

Is there any way of exploding imported DWG and have it not flattened?

The drawing will be of tendons in a bridge segment
I was hoping to draw the tendon using Conceptual mass by picking the Model Line from DWG

[okoeBKLA9]

I draw an sweep in autocad from the spline, attach file to revit and draw sweep by picking lines