4. In the "Edit Template" section, check the box at the top right that says "Expand Widget Templates".

5. Use your browser's search function to find this line:

<div class='post-footer'>

6. Find the 2 lines in your template that look like this:

<div class='post-footer'>
<p class='post-footer-line post-footer-line-1'>

7. Copy and paste the following code between those 2 lines:

<!-- Footer Button Codes BEGIN -->
<div>
<p><span id='footer-buttons'>
<!-- things placed after this line will show on all pages -->


<b:if cond='data:blog.pageType == &quot;item&quot;'>
<!-- things placed after this line will only show on post pages -->

<!-- TwitThis Button BEGIN -->

<a href='javascript:(function(){TwitThisPop=window.open(%22http://twitthis.com/twit?url=%22+encodeURIComponent(location.href)+%22&amp;title=%22+((document.title)%20?%20encodeURIComponent(document.title.replace(/^\s*|\s*$/g,%27%27))%20:%20%22%22),%20%22TwitThisPop%22,%20%22width=600,%20height=500,%20location,%20status,%20scrollbars,%20resizable,%20dependent=yes%22);%20setTimeout(%22TwitThisPop.focus()%22,%20100);%20})()'><img alt='TwitThis' src='http://ajax.twitthis.com/chuug.twitthis.resources/twitthis_grey_72x22.gif' style='border:none;'/></a>

<!-- TwitThis Button END -->

<!-- Do Not Paste Any Code Below This Line -->
</b:if>
</span></p>
</div>
<!-- Footer Button Codes END -->

8. Click the button at the bottom of the page that says "Save Template".

If you get any red errors, leave a comment stating the specific error message, and I will try to help you out. If you get any errors beginning with "bX-", just try again tomorrow. Sometimes Blogger has issues with itself and waiting a bit can resolve them.

also visit http://drsocial.org/forums/topic/318/-/view/post_id/577