Step1:
Go to http://www.facebook.com/share/ and create and customize your button as you like.
After finishing customization copy the code.
Step2:
Now login to youe blogger account then go to Layout >> EDIT HTML then before editing don't forget to check the Expand Widget Box.
Now find the code from the box code (you can click Ctrl+F)
<
div class='post-header-line-1'/>
After the above code, paste the button code you copied in Step1.
If you didn’t find the code above in your template HTML, Then try to find the following code,
<data:post.body/>
And paste the button code before it.
Now you will now see facebook share button on every blog posts.