Did you look at our theming tutorial and the plugin's documentation on http://www.zenphoto.org/documentation/plugins/_plugins---user_logout.php.html? Then you will see how to add php functions to your theme files. I am sorry, but you will have to learn a few things about this if you want to customize your theme. Many plugins are optional and therefore not already implemented on the standard themes to not bloat them. If you know HTML in general adding a function should really not be that difficult.