Developers can now download the new Windows 10 Creators Update SDK Preview to be used in conjunction with Windows 10 Insider Preview (Build 15021 or greater).
The Preview SDK Build 15021 contains bug fixes and under development changes to the API surface area.
This Windows SDK also includes updates and additions to the Windows namespace. See the Microsoft blog post for the full list of API changes under development and new, or updated for this release of the SDK.
The SDK will require Visual Studio 2017 Preview. You can download the Visual Studio 2017 Preview here. The Preview SDK is a pre-release and cannot be used in a production environment. Microsoft suggests developers should only install the SDK on their test machines and if they are working on an application that they need to submit to the store, developers should not install the preview.
The Preview SDK can be downloaded from developer section on Windows Insider here.