This is a video tutorial on creating a 2D car racing game with Unity 5 by the youtuber Charger Games. Here is the first part of the tutorial series in which the 2D project is created with Unity 5:
The author (Raja) is importing the cars as sprites into a project folder in Unity. Then he is positioning the objects.
In the next part of the tutorial he is painting the racing tracks with Inkscape and also imports the images as sprites into the Unity project.
The realization of such a 2D game is well explained and you will get into it very easy even if you are totally new to Unity development. So I recommend the tutorial, visit his channel, follow and begin to create:-)