You have to install Adobe Exchange Panel first. There are two ways to install it:
1. You can launch Adobe Creative Cloud then select Exchange Panel for CS6 to install.
2. You can download Exchange Panel for CS6 from http://www.adobeexchange.com and install it with Adobe Extension Manager CS6.
Then you can launch Photoshop CS6, select "Window"->"Extensions"->"Adobe Exchange" menu item, search "NCS Selector" in the search box at the top right corner of the panel, then install it.