The button Update takes you to: http://msdn.microsoft.com/en-us/jj650015
There you can Download and Install (you need internet access)http://go.microsoft.com/fwlink/?LinkID=320745
Or you can set up an Administrative Install Point (optional), once downloaded use:
SSDTSetup.exe /layout <destination>
Where <destination> is the location you wish to create the administrative install point, 1.8GB space required. Well in my case it downloaded 406MB.
To install use the install point and run SSDTSetup.exe from the <destination> location with no arguments.
Or you can download an ISO (optional)
Choose your venom.
Microsoft SQL Server Data Tools provides an integrated environment for database developers to carry out all their database design work for any SQL Server platform (both on and off premise) within Visual Studio. Database developers can use the SQL Server Object Explorer in VS to easily create or edit database objects and data, or execute queries.