To have a completely new template (design and pages) you would need to delete the current website via Admin->Delete site and start a new site, but you can change the individual elements manually.
To change the background template, go to Design->Background->New background->Library->All, then select the background you prefer. Click `Use this'.
You may need to reposition the menu in the Page Master, and move the items on the individual pages, to fit with the new template.
To change the menu, go to Design->Menu->New menu style->Library, then select the menu you prefer. Click `Use this'.
You can delete pages in Pages->Organise pages, then click on the dustbin beside the page to be removed.
You can add pages in Pages->Organise pages->Add a new page->Choose a page to add.
You can edit the page title in Pages->Organise pages, then edit the text in the appropriate window, and 'Apply'.
Geoff, the Support team