You will need to have installed the Mobile development with JavaScript workload as part of the Visual Studio 2017 installation process. For now, let's assume that you did not install it when you installed Visual Studio 2017 and now need to run the installer again.
You can also run the installer from the New Project dialog screen in Visual Studio 2017. If you collapse the installed templates, you will see a section that allows you to open the Visual Studio Installer.
Go to the Visual Studio website at https://www.visualstudio.com/ and download the installer for the version of Visual Studio you have installed. Also take note that you will need to have Google Chrome installed on your machine in order to launch the Cordova application simulator.