Add the following code in your site, inside the head tag:
<script> function SocialShare(url) { window.open('https://tuiteres.es/share?url=' + url, '', 'height=600,width=800'); } </script>
Then place the share button after changing the URL you want to share to your page HTML:
<button onclick="SocialShare('http://yoursite.com/')">Share</button>