You should already have the cable - it comes with your camera but you may want to buy an extension USB as the cable is quite short!
If you use Lightroom, it already have tethering fro the Nikon built in - I do product photography and all my daily shooting is via tether with Lightroom.
Now, if you don't use Lightroom and you use PC Windows, there's a really good free software (I was one of the early alpha testers) - it works great and even allow you to control your camera from your computer:
Easy to use, free solution for complex camera control | digiCamControl
If you use Mac, they don't have one for the Mac but I run Wiindow7 using VMWare on my Mac and have test DigiCamControl in that environment successfully.
Hope that helps.