First you'll want to install it. There are various implementations. I prefer the one written in C but only because it's the easiest for my environment. Then this guide will walk you through most of what you need to know.
The way I learned how to use SCSS was to reference that guide and then look at Bootstrap's variables and observe how they affected included styles in bootstrap.scss. You'll notice in bootstrap.scss you can comment out the imports you don't need.
First you'll want to install it. There are various implementations. I prefer the one written in C but only because it's the easiest for my environment. Then this guide will walk you through most of what you need to know.
The way I learned how to use SCSS was to reference that guide and then look at Bootstrap's variables and observe how they affected included styles in bootstrap.scss. You'll notice in bootstrap.scss you can comment out the imports you don't need.
There's an extension for visual studio code called Live SASS compiler that does the trick and it's awfully simple to install.
As for a tutorial, the official site has great documentation and it's, I believe, the best place to start.