Nikon D3s is supported in this version of Lightroom.
You should be able to directly import the .Nef image to Lightroom.
If you get any error message, Post it here with Screenshot of Lightroom import window.
As Akash says the D3S is supported out of the box and you shouldn't have any problems.
Have you used an old version of Nikon software to transfer the files? This has been known to corrupt metadata so that Lightroom can't read the files (it's fixable through a third party utility).