In Umbraco CMS, stylesheets and scripts can be created through the Umbraco Backoffice.
In this video, we will show how you as a developer in Umbraco CMS can create this in the Umbraco Backoffice.
Written documentation:
https://docs.umbraco.com/umbraco-cms/...
You can visit the Umbraco Documentation for written guides about Umbraco via this link: https://docs.umbraco.com/