Add this code to “wp-content/themes/frontier/function.php”

if(!function_exists('wp_pagenavi')){
function wp_pagenavi() {	
		global $wp_query;
		$big = 999999999; // need an unlikely integer
		echo paginate_links( array(
			'base' => str_replace( $big, '%#%', esc_url( get_pagenum_link( $big ) ) ),
			'format' => '?paged=%#%',
			'current' => max( 1, get_query_var('paged') ),
			'total' => $wp_query->max_num_pages	) );
		}
}

Add CSS to Custom CSS

.blog-nav {
	float: left;
	clear: both;
	width: 100%;
	height: 40px;
	margin-top: 20px;
}

.blog-nav a.page-numbers {
    border: solid 1px #ccc;
	-webkit-border-radius: 3px;
	-moz-border-radius: 3px;
	border-radius: 3px;
	-webkit-transition: all 0.4s ease;
  	-moz-transition:    all 0.4s ease;
  	-ms-transition:     all 0.4s ease;
  	-o-transition:      all 0.4s ease;
	padding: 6px 10px; 
	margin-right: 5px;
	text-decoration: none;
	color: #403f41;
	font-size: 12px;
	text-transform: uppercase;
}

.blog-nav a.page-numbers:hover,
.blog-nav span.current {
    border: solid 1px #ccc;
	background: #eaeaea;
	-webkit-border-radius: 3px;
	-moz-border-radius: 3px;
	border-radius: 3px;
	padding: 6px 10px; 
	margin-right: 5px;
	color: #403f41;
	font-size: 12px;
	text-transform: uppercase;
}