[Plugin: Post UI Tabs] Missing functions.php?

Hey Guys,
Great plugin. I can’t seem to get it to work on a site I’m currently building. I built the theme myself, which includes header.php, footer.php and index.php. Is there an issue with not having functions.php?

I’m trying to get it to work here:

http://edakalkay.haneestaging.com/clients/

http://wordpress.org/extend/plugins/put/