How to add html to a header.php or footer php.file file

This is probably a stupid question or I feel I should already know this. But here it is...

I want to add my SSL certificate seal in either the header.php or the footer.php file.
The problem is that I only have the apparent html code I'll paste here.

<!-- GeoTrust QuickSSL [tm] Smart Icon tag. Do not edit. -->
<SCRIPT LANGUAGE="JavaScript" TYPE="text/javascript"
SRC="//smarticon.geotrust.com/si.js"></SCRIPT>
<!-- end GeoTrust Smart Icon tag -->

is this doable?

Thanks!