You can install node from here. You want to grab the LTS version, usually the one on the left. This will download an msi file, that will then install node on your system.
The only thing to watch out for when installing Node is to make sure that it is added to your path, and that you include npm. By default, both of these options will be enabled. For best results, install node on your main hard drive (usually C) with your operating system.
To make sure eveything works, you can open a command prompt and type npm. If the command isn't recognized, you've messed up! Otherwise, a help message explaining npm should display.