How do I edit the home page layout header, right bar or footer?
Visit Admin > Layout (tab)
Here you should see a basic diagram of a page on your site, and you can click on any section to edit content in that area.
Head Tag - here you can select the layout that you wish to edit. For example, if your homepage is set to the Default Layout, select Default to edit the content around your homepage.
After selecting a panel to edit, you can click on HTML Editor, (bottom left) to edit using the visual editor.
When finished, click Update (bottom left of corresponding page).
The Update button at the bottom of the Site page (see screenshot below), is only for updating the Left Pane Width