The following tutorial explains how to edit information in the footer area on a Plone 4 website with DomGreen Beanino theme installed.
Green Bean Theme footer is subdivided into two parts: standard Plone footer (1) and Plone colophon with theme credits (2).
To change Plone info (1) you need to customize template: ZMI -> portal_view_customizations -> footer. Press Customize to enable editing of the current footer and change the text. Do not forget to save the changes when you finish.
To change colophon "Powered by Plone & Python": go to ZMI -> portal_view_customizations -> colophon.
Or you can delete/hide/re-order either of footer parts via Manage portlets -> Plone Footerportlets -> footer/colophon.