1. نذهب الى لوحة التحكم ثم تحرير Html ثم قالب 
2. نبحث عن الرمز</body> و نضيف الكود التالى فوقه مباشرة 

<style>
#rocketbacktotop{
background: url('https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7AWJ1J9c4WQ2jqFArIgfD1ZX-xSm0XzoU1AMJo78OL7AFyF9kp4ZO_8Ul4a7SIvM4i9KVOiutI0z6hkIRYFKnlih9IsaRm_Zfdxb3OJon-Qa7RwaPefKOk74vL-9ojN5D4e-SgOzfycbd/s1600/back-to-top-sprite-30224d9b.png') 0 0 no-repeat;
height: 130px;
width: 72px;
padding:5px;
position:fixed;
bottom: 5px;
right: 5px;
cursor:pointer;
    z-indez:1;
}
  #rocketbacktotop:hover{
    background:url(https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7AWJ1J9c4WQ2jqFArIgfD1ZX-xSm0XzoU1AMJo78OL7AFyF9kp4ZO_8Ul4a7SIvM4i9KVOiutI0z6hkIRYFKnlih9IsaRm_Zfdxb3OJon-Qa7RwaPefKOk74vL-9ojN5D4e-SgOzfycbd/s1600/back-to-top-sprite-30224d9b.png)no-repeat;
background-position: 0 -142px;
}
</style>
<!-- Back to top button by Dabourphone -->
<script src='http://ajax.googleapis.com/ajax/libs/jquery/1.10.0/jquery.min.js'></script>
<script type='text/javascript'>
//<![CDATA[
$(window).scroll(function(){if($(this).scrollTop()>100)
{$("#rocketbacktotop").removeAttr("href");$("#rocketbacktotop").stop().animate(
{bottom:"0"},{duration:100,queue:false})}
else{$("#rocketbacktotop").stop().animate({bottom:"30000"},
{duration:8000,queue:false})}});$(function()
{$("#rocketbacktotop").click(function()
{$("html, body").animate({scrollTop:0},"slow");
return false})});
//]]>
</script>
<!-- Code provided to you by dabourphone Blog -->
<a href='#' id='rocketbacktotop'></a>