Add a section in the theme options for the Footer Signup and then add a section in the php for the footer section for it. https://holyfamilyorlando.diocesanweb.org/orlando for reference. 

<div class="footerSignup footerColumn">
  <?= do_shortcode(get_field('newsletter_shortcode', 'options')); ?>
  <p class="signupText"><?= get_field('newsletter_text', 'options'); ?></p>
</div>

[gravityform id=2 title=false description=false] id for the form in this case.