Please Add These Details In Your Site :

1. Upload These files in your website ROOT option

2. Copy these code and add it in "head" tag 


<link rel="manifest" href="manifest.json"></link>

<script type="text/javascript" src="manup.js"></script>
<script type="text/javascript" src="pwabuilder-sw-new.js"></script>
<script type="text/javascript" src="pwabuilder-sw-register-new.js"></script>
<script src="https://www.gstatic.com/firebasejs/7.16.1/firebase-app.js"></script>
<script src="https://www.gstatic.com/firebasejs/7.16.1/firebase-messaging.js"></script>
<script type="text/javascript" src="pwa-custom.js"></script>