how to make wp-pagenavi work

how to make wp-pagenavi work
could someone tell me .many thanks.

This theme doesn’t support WP-PageNavi by default but you can enable it by adding this to Child Theme functions.php file

// Show Wp-PageNavi when it's active
function unite_content_nav( $nav_id ) {
	global $wp_query;
	if ( $wp_query->max_num_pages > 1 ) : ?>
	   <?php /* add wp-pagenavi support for posts */ ?>
		<?php if(function_exists('wp_pagenavi') ) : ?>
			<?php wp_pagenavi(); ?>
			<br />
				<?php else: ?>
		<nav id="<?php echo $nav_id; ?>">
			<h3 class="assistive-text"><?php _e( 'Post navigation', 'twentyeleven' ); ?></h3>
			<div class="nav-previous"><?php next_posts_link( __( '<span class="meta-nav">←</span> Older posts', 'twentyeleven' ) ); ?></div>
			<div class="nav-next"><?php previous_posts_link( __( 'Newer posts <span class="meta-nav">→</span>', 'twentyeleven' ) ); ?></div>
		</nav><!-- #nav-above -->
	<?php endif; ?>
	<?php endif;

And then replacing original navigation function inside index.php (Again do this via Child Theme by copying index.php file over to Child Theme folder)

<?php unite_paging_nav(); ?>


<?php unite_content_nav( 'nav-below' ); ?>

Additionally you might want to apply some styling since it will use default one from WP-PageNavi