It is well known that adding a related posts widget to the bottom of
your posts increases pageviews and lowers your bounce rate. Link Within
is great for this as it adds a thumbnail and is super easy to add to
your blog. So today I’m going to show all you Blogger users how to add
it to your blog.
First of all navigate to http://linkwithin.com
Fill in your blog details on the front page.
Then click on Get Widget.
On the next page click on Install Widget.
It will now take you into Blogger. On this screen choose your blog if
you have multiple ones on your account then click on Add Widget.
Your Linked In widget has now been added to your layout. All that is
left to do is drag the widget from the top of your sidebar to the
bottom.
Voila. That is all there is to it. Now all your posts will have a related posts widget at the bottom.
source : http://girldoesgeek.com/2012/02/add-related-posts-widget-to-bottom-of-posts-blogger.html