The picture you posted is of the WYSIWYG editor, which is only for adding content to the page.
If you want to edit the layout of the page itself you have 2 options -
Minor page edits to appear across all pages on the site - Go to Appearance -> editor -> page.php and then edit the code to suite your needs.
Large page edits to appear on one or two pages -
- Get access to the files
- Duplicate page.php with a different name
- Edit code
When you go to add a new page you should have an option to pick a page template. Choose the page template you just created.