The styling system is accessible only to the site administration and cannot be accessed by users. Changes to site styles affect the design of the forum, posts all use whatever style sheet that the admins have created/managed.
CSS is a coding language, and teaching one how to use CSS is outside of the scope for user to user support on these forums; please point yourself to one of the millions of search engine results for learning CSS
here or the primer
What is CSS? from w3schools.
These forums are here to assist forum admins with the general operation of their sites, we support the admin so they can operate their communities and make changes to their systems; we provide this support as volunteers on these forums. Users of forums should please direct their inquiries to your administration, as they're the only one who can make these changes to their systems, and we operate on feedback.
Posts for support here should be from the forum license holder, which is generally whomever can make filesystem, styling, and database changes which is usually the site owner; we do not delegate to separate support channels. The users posting need to be users capable of making changes.
