Applying Css Resets For A Smooth And Consistent User Experience

beginner question here! how can i apply some css resets like
:where(html) {
--root-font-size: 16px;
scroll-behavior: smooth;
-moz-text-size-adjust: 100%;
-webkit-text-size-adjust: 100%;
text-size-adjust: 100%;
}

:where(*, *::before, *::after) {
box-sizing: border-box;
margin: 0;
padding: 0;
}
tnx