Step 1 : First of all add the below code just before (above) </head>

<style>

#related-posts {
float : left;
width : 540px;
margin-top:20px;
margin-left : 5px;
margin-bottom:20px;
font : 11px Verdana;
margin-bottom:10px;
}
#related-posts .widget {
list-style-type : none;
margin : 5px 0 5px 0;
padding : 0;
}
#related-posts .widget h2, #related-posts h2 {
color : #940f04;
font-size : 20px;
font-weight : normal;
margin : 5px 7px 0;
padding : 0 0 5px;
}
#related-posts a {
color : #054474;
font-size : 11px;
text-decoration : none;
}
#related-posts a:hover {
color : #054474;
text-decoration : none;
}
#related-posts ul {
border : medium none;
margin : 10px;
padding : 0;
}
#related-posts ul li {
display : block;
background : url("http://i299.photobucket.com/albums/mm297/zozuglogger/weed-bullet.gif") no-repeat 0 0;
margin : 0;
padding-top : 0;
padding-right : 0;
padding-bottom : 1px;
padding-left : 16px;
margin-bottom : 5px;
line-height : 2em;
border-bottom:1px dotted #cccccc;
}

</style>
<script src='http://technotrixdebajyoti.googlepages.com/RelatedPostsByRealtrix.co.cc.js' type='text/javascript'/>


Now, Save your template.


Step 2 : Look for <p><data:post.body/></p> in the template (Note: Make sure to "Expand Widget Template" in the Edit HTML page)


Add the code given below, just beneath <p><data:post.body/></p> .

<b:if cond='data:blog.pageType == "item"'>
<div id="related-posts">
<font face='Arial' size='3'><b>Related Posts : </b></font><font color='#FFFFFF'><b:loop values='data:post.labels' var='label'><data:label.name/><b:if cond='data:label.isLast != &quot;true&quot;'>,</b:if><b:if cond='data:blog.pageType == &quot;item&quot;'>

<script expr:src='&quot;/feeds/posts/default/-/&quot; + data:label.name + &quot;?alt=json-in-script&amp;callback=related_results_labels&amp;max-results=5&quot;' type='text/javascript'/></b:if></b:loop> </font>
<script type='text/javascript'> removeRelatedDuplicates(); printRelatedLabels();
</script>
</div></b:if>



Finally, Save Your Template.