From MSDN
The primary method of installing LocalDB is by using the
SqlLocalDB.msi program. LocalDB is an option when installing any SKU
of SQL Server 2012 Express. Select LocalDB on the Feature Selection
page during installation of SQL Server Express. There can be only one
installation of the LocalDB binary files for each major SQL Server
Database Engine version. Multiple Database Engine processes can be
started and will all use the same binaries. An instance of the SQL
Server Database Engine started as the LocalDB has the same limitations
as SQL Server Express
Or you can download standalone SqlLocalDB.msi from the list of available downloads on the SQL Express
downloading page
To locate localdb
instance on your PC simply try to connect to (localdb)\Projects