Step 1 : First enable share buttons for blogger editing the Blog Posts widget from Page Elements section.

Step 2 : Go to "Edit HTML". Click on "Expand Widget Templates"
Step 3 : Find this and remove it:
<b:include data='post' name='shareButtons'/>Note : If you can not find above code, then skip that step.
Step 4 : Now add below code just above the </head> tag.
<script type="text/javascript" src="You are not allowed to view links.
Register or Login">{lang: 'en-US'}</script>Step 5 : Scroll down to where you see below code:
<div class='post-header-line-1'/>Step 6 : Now Copy below "Blogger Sharing buttons" code and paste it just below the above code.
NOTE: If you can't find
<div class='post-header-line-1'/> in your template, paste "Blogger Sharing buttons" code just before
<data:post.body/> .
<b:if cond='data:blog.pageType == "item"'><div class='post-share-buttons' style='float:right;margin-right:10px;'><b:include data='post' name='shareButtons'/></div></b:if>
This will show blogger sharing buttons below post header in blogger post pages..But if you want to show share buttons below blogger post,then paste your code just after <data:post.body/>.
Also if you want to show share button in every page, then remove 2 blue lines form above code.
Step 7 : Now save your template and you are done.