Lighting with hdri and matching backplate
 

Hi guy,
Just wondering if anyone would have any information or know of any articles on how to light a scene with a hdri and matching backplate. What I mean is I'm rendering a car out using just the hdri to light the scene and matching it up with a photo. I can't seem to get shadows on the groundplane as there is no light in the scene, just indirect lighting. I don't really know how to set this up. Any help would be sweet.
Thanks,

Hi guys,
Here's an example of what I'm trying to do.
http://www.hdri-locations.com/
I downloaded the free hrdi and matching backplate from this site.