Download the latest Windows MSI installer corresponding to your Windows version from Nodejs.org. The latest stable 64-bit version at the time of writing this is version 6.9.4. Run the MSI file and follow the instructions. The default install location is C:\Program Files\nodejs\. You may change to your desired location when prompted.
The default installation includes npm (Node Package Manager) and Add to PATH options. You can customize the installation and choose which features you need. If you choose default installation then the installer adds the path to the bin directory, C:\Program Files\nodejs\bin to the Windows PATH environment variable.