JSFiddle - React, Tailwind, and code Playground

HTML

<div class="nav">Nav</div>
<div class="content">Content</div>

CSS

.nav {
    position: fixed;
    left: 5px;
    top: 5px;
    width: 150px;
    height: 400px;
    background-color: pink;
}
.content {
    margin: 0 auto;
    width: 400px;
    height: 800px;
    background-color: orange;
}