If the contour lines in the AutoCAD file are in 3D (in other words, have a Z value if you run the ID command on them), then you need to integrate the DWG file to find what contours are on.
In Revit Architecture you can then IMPORT the DWG file, go use the Topography tools to and create a surface using import. After selecting the import, it will ask you to specify the layer with the contours on them. Upon finishing the surface you will have a topography surface within Revit, the opportunity to add site components (such as trees etc), as well as label contours etc. If will naturally be available in sections, 3D views etc.
If your DWG file is not in 3D, i.e. a flat surface - first check with your surveyor, a 3D file may be available or a points text file (which Revit can also use may be available). If not, then you will need to move the contours to the correct elevation manually, or if you have Civil 3D you can use the enhanced tools on the Toolbox panel.
Hope this is useful.
