Hi Martin,
are you sure you bought the LayTheme and not the Gridder Plugin?
Here is Laytheme
http://laytheme.com/
You install it as a theme
Here is the Lightbox plugin which works ONLY with Laytheme
http://laytheme.com/lightbox.html
You install it as a plugin
Here is the LayGridder which is a Wordpress plugin which you do NOT install with Laytheme but with an empty Wordpress installation. It is not connected to Laytheme
http://laygridder.com/
You install it as a plugin.
If you made the wrong purchase – let us know. We can fix that.
Best!
Marius