Look for <td class="button" in the HTML of the email you’d like to modify and add the following after:
<td class="button" align="center" width="280">
{% assign cta = "advocate_offer_email_button_1" | localize: "Share Now" | replace: '"', '"' %}
<a href="https://yoursitename.com/pages/share" tar
get="_blank" title="{{ cta }}">
{{ cta }}
</a>
</td>
<tr>
<td class="ie-reset" height="30"> </td>
</tr>
<td class="button" align="center" width="280">
{% assign cta = "advocate_offer_email_button_2" | localize: "Share Now" | replace: '"', '"' %}
<a href="https://yoursitename.com/pages/share" target="_blank" title="{{ cta }}"> {{ cta }}
</a>
</td>
</tr>
Make sure to add the name for each CTA in the Editor.