SOLVED:
I added the following to functions.php.

/*
 * Add WooCommerce Login/Logout to avia2 menu
 */
add_filter( 'wp_nav_menu_items', 'add_loginout_link', 10, 2 );
function add_loginout_link( $items, $args ) {
    if (is_user_logged_in() && $args->theme_location == 'avia2') {
        $items .= '<li><a href="'. get_permalink( wc_get_page_id( 'myaccount' ) ) .'">My Account</a></li>';
        $items .= '<li><a href="'. wp_logout_url( get_permalink( wc_get_page_id( 'myaccount' ) ) ) .'">Log Out</a></li>';
    }
    elseif (!is_user_logged_in() && $args->theme_location == 'avia2') {
        $items .= '<li><a href="' . get_permalink( wc_get_page_id( 'myaccount' ) ) . '">Log In/Register</a></li>';
    }
    return $items;
}