Theme options is a widget included with Arden. To open it, go to Blogger → Layout and click the Theme options widget.
Inside the widget you will see these settings:
sidebar-blog: no
sidebar-post: no
sidebar-page: no
sidebar-category: no
sidebar-search: no
sidebar-archive: no
show-author: yes
contact-path: /p/contact.html
Choose where the sidebar appears
Change a page type from no to yes when you want the optional sidebar to appear there. The homepage is always full-width and does not use a sidebar.
Show or hide author information
Keep show-author: yes if you want the author name and available author information to appear on posts. Change it to no if you prefer to hide them.
Choose the Contact page
The contact-path line tells Arden which Blogger page should show the built-in Contact Form. Leave /p/contact.html if that is the address of your Contact page. If your published Contact page has a different address, replace only that part with the address Blogger gives you.
The sidebar items remain available in Layout even when the sidebar is hidden on a page type.