If u want to style your application in where your moduler version is below 9 you can do it by creating a example.scss file in theme>web>scss>app>example.scss and you want to import this example.scss file in custom.scss file. and you need to install and run the calypso for the compilation of scss to css.
or if u are styling your application in modular versions 9 or 9+
you need to add your example.scss file in themesource>UIsource>web>example.scss and you need to import this file in main.scss file and no need to use the calypso above 9 versions because compiler is inbuilt for this modulers.
Hope this information helps you.
You need to add a ‘public’ folder to your UIsource/module and then your example.scss file in themesource>UIsource>public>example.scss and you need to import this file in main.scss file. To enable this you have to right-click the ‘Styling’ and select ‘Show styling for’ and ‘App and all modules’.