From the backstage, select or from the bottom drawer of Conceptualize mode > Categories and Models select Attach external file.

The Attach external data dialog displays.

The Attach tool is designed to attach and detach the following file types:

• ContextCapture 3MX or 3SM file (.3mx, .3sm)
  Note: Roadway Targeting and Clipping does not operate on 3D 3SM terrains.
• Vissim animation export file (.ani.txt)

Once the file is attached it can be turned on or off.

Remove the file from the bottom drawer by selecting the Detach button.