How to Add a Login/Logout Link to Your WordPress Genesis

functions.php

<?php // add everything except for this opening line to your functions file
add_filter( 'wp_nav_menu_items', 'sp_add_loginout_link', 10, 2 );
function sp_add_loginout_link( $items, $args ) {
	// Change 'primary' to 'secondary' to put the login link in your secondary nav bar
	if ( $args->theme_location != 'primary' )
		return $items;
	if ( is_user_logged_in() ) {
		$items .= '<li class="menu-item"><a href="'. wp_logout_url() .'">Log Out</a></li>';
	} else {
		$items .= '<li class="menu-item"><a href="'. site_url('wp-login.php') .'">Log In</a></li>';
	}
	return $items;
}