From the Website Portal, navigate to Content > Design > Web Pages.
Find the Web Page you want to edit in the list and either click the Web Page name hyperlink or the "Edit" icon in the actions column in the list view.
The following tabs are only displayed when an existing Web Page is being edited:
The SEO Tab lets you view and edit the page's SEO related information such as the Meta Title, Meta Description, Meta Keyboard, whether the page is indexed by search engines or not, and whether to allow the page to be marked as No Follow.
The Header/Footer Tab lets you view and edit the page specific header and footer code.
When you are done editing, click "Save and Close" or "Update" if you still are working on the page and you just want to save your progress.