Adding class to menu anchors

I’m converting a Bootstrap template into a WordPress theme and I’m trying to figure out how to add a class to the anchors within a menu.

The menu’s registered in functions.php, and it’s displaying as expected. I’ve already added a few classes to the list, but I’m not sure how to target the anchors.

This is my existing function to call the menu:

<?php $defaults = array('menu' => '3', 'menu_class' => 'nav navbar-nav navbar-right');
    wp_nav_menu( $defaults );
?>

Any help would be appreciated!