The .NET Framework 4.6 RC is the latest version, which exposes new APIs that you can use in your app or library. As a developer, you can make use of the new framework to run existing apps.
You will be able to target .NET Framework 4.6 RC using Visual Studio 2015. However, Microsoft recommends developers to target .NET Framework 4.5.2 by default with Visual Studio 2015 since it has been deployed globally. Moreover, you should make use of .NET Framework 4.6 RC only if you specifically need the new APIs included with the latest version.
You can target the .NET Framework 4.6 RC by changing the Target Framework for your app or library, under Project Properties.
It is also possible to target the .NET Framework 4.6 RC in Visual Studio 2012 and Visual Studio 2013 by installing the .NET Framework 4.6 RC Targeting Pack or installing Visual Studio 2015 on the same machine.
In the Build machines, you need to install the .NET Framework 4.6 RC Targeting Pack. Microsoft has published .NET Framework and Applications Guide that describes several options for the successful deployment of .NET Framework.
If your users have not installed the .NET Framework they will be prompted to install it before attempting to run the app or project. The users will be automatically redirected to the download location for the required version of the .NET Framework.