Windows Phone SDK
The Windows Phone development tools include everything you need to develop apps and games for Windows Phone.
To install the SDK, click the Download button (below) and then select the option to Run. From there, you simply need to follow the instructions on the screen.
Windows Phone 8.1 development tools
The Windows Phone 8.1 development tools are included with Visual Studio 2013 (Update 2 or later). If you already have Visual Studio 2013 installed, use the download link to install Visual Studio 2013 Update 2 RC:
Windows Phone 8.1 Emulators
The Windows Phone 8.1 Emulators package adds six emulator images to an existing installation of Visual Studio. With this update installed, developers can test how apps will run on phones running Windows Phone 8.1. This update requires Visual Studio 2013 with Update 2 or later.
The Windows Phone SDK 8.0 enables you to develop apps for Windows Phone 8 and Windows Phone 7.5 devices.