how can this JS be installed on an Atahualpa site?
 

Please see the script at:

http://www.echoecho.com/toolfloatinglayer.htm

I'd like to use it in an Atahualpa-based site.

Here's an example of how one site is using it (non-WordPress)

http://currykitchen.net/menu2.php

I can't see what they are using as a shopping cart. Or is it all simply JS?