You can edit file templates/jf_creativia/templateDetails.xml, add field at line 92:
<field name="instagram" type="text" default="" size="30" label="Instagram URL " description="" />
Edit file templates/jf_creativia/index.php, at line 323 add:
<?php if ($this->params->get('instagram') != '') : ?>
<li><a target="_blank" id="instagram" title="Visit us >params->get('instagram') ?>">
<img src="<?php echo $this->baseurl ?>/templates/<?php echo $this->template ?>/images/social-icons/instagram.png" alt="" />
</a></li>
<?php endif; ?>
In Template Manager, enter Instagram URL and save.
joomfreak