The SDK is available from GitHub or it can be installed from nuget.org. The README on GitHub offers lots of details about installing or building from source code. The SDK is built with .NET 4.5 but you can easily build with .NET 4.0 if needed. It comes with a unirest-net implementation of IHttpFacade - the UnirestHttpFacade class. You can also define your own implementation to use with the DreamFactory API by providing a custom IHttpFacade.
Let's look at a few examples of how to authenticate to your DSP and make some CRUD calls to its default MySQL database. There's demo code available in the GitHub repo for all of these functions.