The final release of DirectX 12 and Windows 10 is months away but if you're itching to test your system's DX12 theoretical performance today, here's how you can do it.
First, you'll need to have the 64-bit version of the Windows 10 Technical Preview installed. The 32-bit version is not supported. Earlier preview builds had DirectX 12 components aboard but it will take the latest one (build 10041) to enable the DX12 functionality. If haven't installed Windows 10 yet, here's everything you need to get it up and running.
Once you've installed it, check the version number by looking in the lower right hand corner of the screen. It should say "Windows 10 Technical Preview Evaluation Copy, Build 10041." If you're running a previous build, you'll need to update the system.