Check your Camera Raw workflow options (the link at the bottom of the Camera Raw screen). You can change from 8-bit to 16-bit there.
I do not know how to get to Camera Raw.
Camera Raw is a plug-in that is accessible from either Bridge or from Photoshop. I prefer to look at my raw images in Bridge and then open them directly from Bridge into Camera Raw. You can make that choice from the Bridge preferences, general tab:
After you make that choice and click OK to save the preferences, then all you have to do is double-click on one of your raw images. It will then open in Camera Raw. At the bottom of the Camera Raw screen you will see the following:
When you click on that hyperlink you will see where you can change from 8-bit editing to 16-bit. However, all of that isn't going to change the image to a 16-bit image. I just did some experimenting. Apparently there is an option in your camera settings where you can choose the bit depth for your raw images. You will have to find that setting and change it. More than likely it will be something like 12-bit or 14-bit. At least those are the choices I have with my Nikon D 7100. then you can open those images in Camera Raw and edit them in a 16-bit editing workspace.