The 1.6.6 update brings official support to the Nikon D7100 and D5100. These cameras use a USB cable with special connectors that are custom to Nikon. The cable that came with your camera will work or they can be purchased as well, but it is not a standard USB cable.
The update allows also LCD image playback on the back of the camera for newer Nikons. It's still not available on older models, but the latest and greatest Nikons allow images to be seen on the back when connected to the CamRanger. You do need to have the connection within the CamRanger app set to "Cam".