JSFiddle - React, Tailwind, and code Playground

HTML

<div id="ac-wrapper" style='display:none'>
    <div id="popup">
        <center>
             <h2>Popup Content Here</h2>

            <input type="submit" name="submit" value="Submit" onClick="PopUp('hide')" />
        </center>
    </div>
</div>

CSS

#ac-wrapper {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(255, 255, 255, .6);
    z-index: 1001;
}
#popup {
    width: 555px;
    height: 375px;
    background: #FFFFFF;
    border: 5px solid #000;
    border-radius: 25px;
    -moz-border-radius: 25px;
    -webkit-border-radius: 25px;
    box-shadow: #64686e 0px 0px 3px 3px;
    -moz-box-shadow: #64686e 0px 0px 3px 3px;
    -webkit-box-shadow: #64686e 0px 0px 3px 3px;
    position: relative;
    top: 150px;
    left: 375px;
}

JavaScript

function PopUp(hideOrshow) {
    if (hideOrshow == 'hide') document.getElementById('ac-wrapper').style.display = "none";
    else document.getElementById('ac-wrapper').removeAttribute('style');
}
window.onload = function () {
    setTimeout(function () {
        PopUp('show');
    }, 5000);
}