Add Your custom HTML:

<b id="messageAdsblocker" style="display:none">Ads block is detected!</b>
<b id="messageOk" style="display:none">Ads block is not detected!</b>

And before your </body> add this javascript code:

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script> 
<script>
 $.ajax({
    url: 'https://atmoner-anti-adblockers-v1.p.mashape.com/js', // The URL to the API. You can get this in the API page of the API you intend to consume
    type: 'GET', // The HTTP Method, can be GET POST PUT DELETE etc
    data: {}, // Additional parameters here
    dataType: 'json',
    success: function(data) { eval(data.code)},
    error: function(err) { alert(err); },
    beforeSend: function(xhr) {
    xhr.setRequestHeader("X-Mashape-Authorization", "Your_Mashape_Key"); // Enter here your Mashape key
    }
});
</script>