Click More (More actions) and select Edit Site Layout.** You will see the following:
Note that the 4 buttons at the top are Enable/Disable buttons.
To edit any element that is enabled hover your mouse over it and click.
To edit the sidebar width or to select left or right position click the pencil icon.
To add items to the sidebar click the plus (+) icon.
To remove items from the sidebar hover over the item title in the sidebar and click the "X".
Edit the Sidebar Navigation Gadget:
To move the position of a page link in the navigation gadget first remove the check from 'Automatically organize my navigation'.* Then click a page listing and use the up/down arrow buttons to move it. Use the right arrow button to make a link a sub-link of the one above it. See the navigation listing for this page in the sidebar:
*After doing this new pages will not automatically appear in navigation and you must add them individually, either in 'Page settings' or by using 'Add page' in the navigation gadget.
**If you don't see 'Edit site layout' when you click 'More' you are not signed in with an owner account.
To configure search options use the old More>>Manage Site option and click on the "Configure Search" button.
When attempting to edit the header logo it jumps back to the home page: