Adding Whatsapp feature in any website like wordpress, laravel, codeigniter, php any other is very easy.
Just copy and paste below code
<a href="https://wa.me/9989xxxxxx" target="_blank">
<img src="http://localhost/wordpress/wp-content/uploads/2022/03/whatsapp-logo-icone.png" width="20px"></a>
In above code 9989xxxxxx in place of this number give your number, then customers can directly able to chat with you.
Just we are chatting purpose only we are integrating it we are not going to save this whatsapp chat details.
You can place the icon in any where in the website like Home page or footer or contact us page as you like.