JSFiddle - React, Tailwind, and code Playground

HTML

<div class="wrapper">wrapper
    <div class="sidebar">sidebar</div>
    <div class="main">main</div>
</div>

CSS

body{background: #ccc;}
.wrapper {
width: 650px;
    background: green;
}

.sidebar {
    background-color: #ddd;
    width: 300px;
    position: fixed;
 
}

.main {
float: right;
    background-color: yellow;
    width: 300px;
    height: 1400px;
}