How can I style a FluentUI component in Blazor?

I'm new to FluentUI. I just started a MAUI/Blazor hybrid app and I'm struggling to apply the styles that I want to my FluentUI components.

Styling works when I use inline styling.

For example:

<FluentHeader Style="background-color:blueviolet">    Header text</FluentHeader>

and this works.

But when I add a class to the component and then try to style it using mycomponent.razor.css, it does not work. Am I missing something about FluentUI? I have read the documentation and I found things like design tokens but still did not try those.

Can someone please tell me how to do this? Thanks