JSFiddle - React, Tailwind, and code Playground

HTML

<p class="contentbutton" id="setup" onclick="expand ()">SETUP</p>

CSS

.contentbutton {
    border-radius: 40px;
    background: #d6d6d6a1;
    padding: 20px; 
    width: 60%;
    height: 20px;  
    text-align: center;
    font-family: 'Montserrat', sans-serif;
    font-weight: bolder;
    margin: 15px;
    box-shadow: 0px 3px 7px #7979793d;
    text-shadow: 0px 2px 3px #79797967;
    -webkit-transition:0.5s;

  }

.contentclicked { 
  width: 90%;
  height: 200px;  

}

JavaScript

var set     = document.getElementById("setup")

function expand() {
    set.classList.toggle('contentclicked');
}