SASS (Syntactically Awesome Stylesheet) is a CSS pre-processor which helps to reduce repetition with CSS and saves time. It is more stable and powerful CSS extension language that describes style of document structurally. .I refer useful and helpful post about How to use Sass.I think it will help you.
https://www.mindstick.com/Articles/1478/how-to-use-sass-file
http://thesassway.com/beginner/how-to-structure-a-sass-project