Once the project is generated with Angular/CLI, set default style extension:

ng set defaults.styleExt scss

After you have generated a new component:

ng g c MyComponent

you will see MyComponent.scss in your MyComponent folder.

If you open the scss-file, WebStorm will ask you, if you want to add file-watchers for this type of extension. This procedure is normally not necessary, because angular/cliwill generate and update your project automatically.

Anyway, If you want to add file-watcher for SCSS (on McOS):

  1.  brew install ruby
  2. gem install sass

WebStorm will automatically recognize the installation path (on McOS /usr/local/bin/scss).