1.Log in to your dashboard--> layout- -> Edit HTML
2.Click on "Expand Widget Templates"
3.Scroll down to where you see this:
4.
After the above code , copy and paste the code below:
| <a  class='timestamp-link'  expr:href='"http://www.stumbleupon.com/submit?url=" + data:post.url +  "&title=" + data:post.title' title='permanent link'><img  style="padding: 0; border: none;"  src="http://cdn.stumble-upon.com/images/32x32_su_round.gif" alt="Stumble  Upon Toolbar" align=""/></a> | 
5.Click on "Save Templates" and refresh your site.
It will look like this.
 
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