Add the code below in your theme’s function.php file;
/* Return FB Like Button below Mashshare share buttons
*
*/
function returnFBLike($html){
return $html = $html . '<div class="mycustomLikeButton"><iframe width="300" height="150" style="border: none; overflow: hidden; width: 250px; height: 80px;" src="//www.facebook.com/plugins/like.php?href=https%3A%2F%2Ffacebook%2Fmashshare.net&width=230&layout=standard&action=like&show_faces=true&share=false&height=80&appId=1602942513258261" scrolling="no" frameborder="0" allowtransparency="true"></iframe></div>';
}
add_filter('mashsb_output_buttons', 'returnFBLike');If necessary adjust width, APP ID (or remove it) and URL to your needs.
Alternatively you can use the facebook like button generator: https://developers.facebook.com/docs/plugins/like-button
