1. Go to this Link, to get the latest update.
2. Download the latest update, following the link above. Note: do not install, simply download it.
3. Once the package is downloaded, an iso file will be available on your hard disk. For Visual Studio 2012 update 2 or earlier, the iso won’t be built for you, and you can try below command instead:
However, for VS2012 update 3, the ISO is made for you!
Enjoy and happy coding!