How to Add a Authorize.Net Seal To Your Website
1. Storefront CMS > CMS Features > Website Pages 
2. Locate sub-footer.html > click edit 
3. Enter snippet code in the Page Contents section. Snippet code below screenshot 
Here is the code that you are to add to your Sub Footer webpage:
<br>
<center><!-- (c) 2005, 2020. Authorize.Net is a registered trademark of CyberSource Corporation --> <div class="AuthorizeNetSeal"> <script type="text/javascript" language="javascript">var ANS_customer_id="55abfed2-3aff-47fc-b419-1d9c980a99d9";</script> <script type="text/javascript" language="javascript" src="//verify.authorize.net:443/anetseal/seal.js" ></script> </div> </center>