Steps to add jQuery Scroll To Top Button to Blogger:

1. Login to Blogger.

2. Navigate to Design > Edit HTML.

3. Backup your Blogger template by clicking Download Full Template and keep it safe in your computer. Remember, its better to do this everytime you do a template edit to be on the safe side in case you encounter any problem

4. Find this code within the blogger template code(using CTRL+F):

</head>

5. Paste the following code just before the above line.

<script src='http://ajax.googleapis.com/ajax/libs/jquery/1.3.1/jquery.min.js' type='text/javascript'/>

<script type='text/javascript'>
//<![CDATA[

$(function(){

$('a[href*=#top]').click(function() {

if (location.pathname.replace(/^\//,'') == this.pathname.replace(/^\//,'')
&& location.hostname == this.hostname) {

var $target = $(this.hash);

$target = $target.length && $target || $('[name=' + this.hash.slice(1) +']');

if ($target.length) {

var targetOffset = $target.offset().top;

$('html,body').animate({scrollTop: targetOffset}, 1000);

return false;

}

}

});

});
//]]>
</script>

6. Find this code within the blogger template code(using CTRL+F):

<body>

7. Replace the above tag with the below one.

<body id='top'>

8. Find this code within the blogger template code(using CTRL+F):

</body>

9. Paste the following code just before the above line.

div id='goingtop'>
<a href='#top' title='Go Top'><img src='https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjFKHjpXY2tXBsHCEr5JUv7epmTm4ZKNvkCgoOxCreUGd1_Oz6r25E1yQ3ykdPtApK61h1hGNWGeQxU72HU2ZYwurivFGjPqkYCITA23eY9e1DLJTV9ot_OTUkuhTgG1H8PgW94cThtaSSr/' style='right:20px; bottom:20px; position: fixed;'/></a></div>

You can use any other image in place of the above one(in bold).

10. Click on Save Template. You're done.