How can I customize widgets with tailwind?

I wrote this in the my theme.css file, but I cant seem to render it in my widget's blade file

.fi-wi-background {
    background-color: #ff0000;
    background-size: cover; 
}

.fi-wi-background {
    background-color: #ff0000;
    background-size: cover; 
}

.fi-wi-background {
    background-color: #ff0000;
    background-size: cover; 
}

.fi-wi-background {
    background-color: #ff0000;
    background-size: cover; 
}