If you are in single post display you may find a [single.main.php] in your skin folder.
In that file or any other relevant file that displays a post you may find

<?php
	// ------------------- PREV/NEXT POST LINKS (SINGLE POST MODE) -------------------
	item_prevnext_links( array(
			'block_start' => '<table class="prevnext_post"><tr>',
			'prev_start'  => '<td>',
			'prev_end'    => '</td>',
			'next_start'  => '<td class="right">',
			'next_end'    => '</td>',
			'block_end'   => '</tr></table>',
		) );
	// ------------------------- END OF PREV/NEXT POST LINKS -------------------------
?>

You can place this at the end of the post or item

The exact location is dependent on the file and where exactly you want it.

thanks much