In single.php under this line:

<? if (have_posts()) : while (have_posts()) : the_post(); ?>

Use something like this:

<ul id="next_prev">
<li class="left">
<?php previous_post_link('%link', 'Previous', TRUE); ?>

<li class="right">
<?php next_post_link('%link', 'Next', TRUE); ?>

<div class="clear"></div>

And a corresponding style in style.css:

ul#next_prev {
background:transparent;
color:inherit;
list-style-type: none
}
ul#next_prev .left { float: left }
ul#next_prev .right { float: right }

I know about that. Where in your theme?

Here is the official documentation for adding those features... http://tinyurl.com/6oj9x6

Could you please describe the best way to go about adding next and previous
links on blog posts?