You need the ".ens" format file that defines the style. There are a list of thousands of styles available for download directly from Endnote at http://endnote.com/downloads/styles/.
Once you have downloaded the style, you can add it to EndNote by copying the downloaded file to the Style folder that is within your EndNote installation. Typically EndNote is installed at C:\Program Files (x86)\EndNote X7\ or C:\Program Files\EndNote X7\.
Note: You must be an administrator of the your computer to install the new style.
