Load a polylines from ArcInfo ASCII GEN file.
You can simply open GEN files or choose the Import from file command from the context menu for Drawings tree item.
To write the contours to GEN file:
1. Create the contour maps.
2. Choose the Copy isolines to Drawings command from the context menu for Isolines tree item
3. Choose the Save to file command from context menu for Drawings tree item and save the lines as GEN format.