JSFiddle - React, Tailwind, and code Playground

HTML

<div class="norm">Font Weight 400</div>
<div class="semi">Font Weight 600</div>

CSS

@import url(https://fonts.googleapis.com/css?family=Source+Sans+Pro:400,600);

body {
  font-family: 'Source Sans Pro', sans-serif;
}

.norm {
  font-weight: 400;
}

.semi {
  font-weight: 600;  
}