Add next and previous link to oulipo theme

the functions are:
https://codex.www.ads-software.com/Function_Reference/next_post_link
https://codex.www.ads-software.com/Function_Reference/previous_post_link

example use (from twenty ten):

<div id="nav-above" class="navigation">
					<div class="nav-previous"><?php previous_post_link( '%link', '<span class="meta-nav">' . _x( '&larr;', 'Previous post link', 'twentyten' ) . '</span> %title' ); ?></div>
					<div class="nav-next"><?php next_post_link( '%link', '%title <span class="meta-nav">' . _x( '&rarr;', 'Next post link', 'twentyten' ) . '</span>' ); ?></div>
				</div><!-- #nav-above -->

you would need to add this kind of code to single.php of your theme.