In Civil 3D, contours are not individual objects like they were in LDT. Here, contours are part of the surface object, and are displayed by choosing a style that displays contours.
If you are digitizing polylines you can add these to a surface similar to how you would do it in LDT. Assign elevations to your polylines; create a new surface; right-click on breaklines, choose Add; select your polylines; then choose a style (or edit the current style) to display the contours.
Otherwise you can still use LDT to create contours from polylines, and block them into C3D - they just won't be intelligently linked to a surface. Which may be fine if you don't need surface data...
Hope this helps...
Charlie Ogden, PE - Application Engineer
(800) 336-DESK (3375)
Microdesk is the only Autodesk Premier Solutions Provider (PSP) in the Northeast to earn both Civil/Mapping & Architectural Specialist distinctions.