Open a command line tool and change to the directory fileadmin/bsdist/ of your new TYPO3 instance.
1. Install the node packages.
2. Use bower to install the main components.
Font Awesome will not be installed in the default configuration! See file bower.json.
After sucessfully installing the node packages and bower components there are two new folders in fileadmin/bsdist.
3. The grunt task init copies files from bower_components/ to lib/ and executes all tasks (full).
Or use tools in your IDE...
The files in lib/ - i.e. bootstrap scss - are not processed with the default task. Only the task group named full sassifies and concats the resources in lib/.