To download the admin install go to http://msdn.microsoft.com/en-us/data/hh297027, download the ssdtsetup executeable for SQL Server 2014, and also vs2010, vs2012, vs2013. From the command prompt run ssdtsetup /layout <destination> where <destination> is the path of the USB stick / network / local drive you want to install to.
This may take a while to download the full install files.
If that’s all a bit to hard just smell this cool SSDT feature here http://msdn.microsoft.com/en-us/library/dn266029(v=vs.103).aspx.
The entry point is pretty simple, just right click your database and select Database Comparison.