Click the above link to download .NETScript for Revit (this package is tested for Revit 2014 64 bits).
After downloading the zip package, unzip it to a folder. There are two files: NetScript.Revit.dll & NetScript.addin
Go to Revit 2014 plugin folder at C:\ProgramData\Autodesk\Revit\Addins\2014, copy NetScript.addin to there.
Use the text editor, open NetScript.addin, go to line 5, change the Assembly location to your folder that stores NetScript.Revit.dll