1. Login to your Blogger Account and go to Design > Edit HTML
and click on the check box which says “Expand Widget Templates”
2. Look for <data:post.body/> and immediately after that place the following code.
<b:if cond='data:blog.pageType == "item"'>
<iframe allowTransparency='true' expr:src='"http://www.facebook.com/plugins/like.php?href=" + data:post.url + "&layout=button_count&show_faces=false&width=100&action=like&font=arial&colorscheme=light"' frameborder='0' scrolling='no' style='border:none; overflow:hidden; width:450px; height:40px;'/>
</b:if>
This code will show the Like Button on Post pages only. If you want to display it everywhere, then remove the two lines of code in red.
3. Save the template and you should see the Like Button Below each of your posts.
src: http://www.bloggerplugins.org/2010/04/facebook-like-button-for-blogger.html