Hello, Ms Johnson;
you can add what you want in the footer, as long as you keep the original 4Homepages Copyright.
You will find it in "includes/page_header.php". In my version, 1.7.4, it is located by the line #122:
<p id="copyright" align="center">
Powered by <b>4images</b> '.SCRIPT_VERSION.'
<br />
Copyright © 2002-'.date('Y').' <a href="http://www.4homepages.de" target="_blank">4homepages.de</a>
</p>
If you want to add keywords describing your site to indexing robots, edit templates/your_template/header.html and make changes by adding:
<meta name="keywords" content="write your keywods here">
For instance:
<meta name="keywords" content="PHP, MySQL, bulletin, board, free, open, source, smf, simple, machines, forum">
As you can see here, using your browser and "view source".