To add Entity Framework 5 reference in Visual Studio 2012, you’ll need to install EF5 NuGet package.
In the project to which you want to add EF5 reference, right click References and select Manage NuGet Packages.
|Go to Online -> All, select EntityFramework and click on Install.|
|Accept the licence agreement and wait for the installer to finish. You’re all set to start using EF5 in your project.|