Adding "No Follow" to a line of code

Hello,
Just wanted to get some examples and/or opinions and/or options on the best way to include a rel=”no follow” within the lines of code below.
Thank You.

<li class="bmnm-sign-in"><a class="logout" href="<?php echo wp_logout_url( bp_get_root_domain() ) ?>"><?php _e( 'Sign Out', 'buddypress' ) ?></a></li>
   <?php else : ?>
   <li class="bmnm-sign-in-join">
     <a href="<?= wp_login_url() ?>"><?php _e( 'Sign in', 'buddypress' ) ?></a>
<?php if ( bp_get_signup_allowed() ) : ?>
   <?php printf( __( ' / Join <a href="%s" title="Create an account"></a>', 'buddypress' ), site_url( BP_REGISTER_SLUG . '/' ) ) ?>
<?php endif; ?></li>