So if you look at your config and you see what bootstrap is actually referencing, so github twitter-bootstrap, bootstrap, and then the version number, we can compare that to where the actual CSS file we want lives, which is github, which matches github. Twitter-bootstrap, the version number, CSS, and bootstrap CSS. So we know that bootstrap refers all the way up into this, which matches here, so we just have to append CSS and bootstrap.css.
So we'll say /CSS/bootstrap.css!, hit save, and now we're loading it locally. You can also do this from, instead of just doing a system import here, if I just want to load my main app.js and then in my app.js I want to import that file and make sure to include the bang there, you can see that that will load it as well. So if I delete this line, hit save, you can see the styles will go away, undo, hit save, and you can see that the styles are back.