1.3.1 - Setup Data Required
Step Description:
You must have at least two alignments that intersect each other only once in your drawing. This is the minimum requirement to create a basic 2D object using the Intersection Design Wizard. To create a more realistic intersection model, you will need road geometry and surface data.

AutoCAD Civil 3D 2012 User's Guide reference:
User's Guide - Corridor Modeling - Intersections and Roundabouts - Intersections - Creating Intersections - Before You Begin
For more information watch the video below:
Create Intersection (WMV)