To allow us to compile source files into production, we now need to download the Bootstrap source files and install them on our local machine. Head to the following URL and download the Bootstrap source files: http://v4-alpha.getbootstrap.com/getting-started/download/.
Once you've download the files, unzip the package and move the directory to where you want it to live on your computer. If you just want to leave it on the desktop for now, that is fine. You can safely move the project around before or after editing it. The next thing you need to do is install the project dependencies. First, navigate to the root of the download package in the Terminal. It will likely be called something like bootstrap-4.0.0-alpha.2. Once you are there, run the following command to install the files:
$ npm install
If you get any type of error, try including sudo at the beginning of the command.