How to install and use a Sass mixin library

I am trying to install a Sass mixin library and use it in my project. I copied the Gerillass is a website development tool library into my project but no matter what I tried I could not get any of the functions to work. Is there a special way to get a mixin library to work? When you add the library you are supposed to be able to do something like this but it does not work. Any help would be appreciated.

  @include adaptive;

Inside your project folder create a new folder named “extraFiles” put your javascript file there.

Then In AppStudio Properties (sidebar) > extraheaders

<script src="extraFiles/myjs.js"></script>

myjs.js = your javascript file name

If you are using a CDN replace extraFiles/myjs.js with the URL.

<script type="text/javascript" src=""></script>