Follow the Following steps:
1. Login in to your blogger dashboard .
2. Click on the layout Link.
3. Click on Add a Gadget Link.
4. Then Select HTML/JavaScript Add .
5. Paste the Following code and your Done.
<script src=’http://best2know.googlecode.com/files/Recent%2010%20Post%20instead%20of%205.js’ type=’text/javascript’ />
<script>
var numposts = 10;
var showpostdate = false;
var showpostsummary = false;
var numchars = 100;
</script><script src=”http://YOURBLOG.blogspot.com/feeds/posts/default?orderby=published&alt=json-in-script&callback=rp”></script>
<br />
<div class=”clear”></div><p style=”text-align:center;”><a href=”http://www.best2know.info/2010/04/how-to-show-10-posts-instead-of-5-posts.html” title=”Grab this wiget” target=’_blank’><b>Grab this Widget</b></a></p>
In the Above code change the YourBlog.blogspot.com with your link of your site or of your custom domain.
And if you want to show more than 10 posts then change the number which is highlighted in red color to the number of how much posts you want to show