All the instructions to install your DK2 with the proper software is all in the instructions manual that came with your kit… (If only people actually read it :\ )
But I guess, I’ll help you out a bit. You can download and install all the required software here:
https://developer.oculus.com/downloads/
Download the Oculus SDK and Oculus Runtime for <Your system> So Windows for Windows, OSX for Mac, and Linux for Linux.
The Oculus Unity Intergration is something you need when you develop Oculus games with Unity. Although I’m not sure if you also needed it to run Oculus Unity games.