In vue/cli app changes in main.scss are not applied

I created @vue/cli 4.0.5 app with scss option and found empty file
I added some style definitions to it and expeted they would be applied on my pages.
Which steps have I to apply my style definitions on my pages?

I did not find any main.css in my project, as I expected to attach it in src/App.vue file like:

  @import './assets/styles/yourstyles.css';

Which is valid way ?