Can anybody tell me how to navigate to "Operations: customize" section so that I can customize the page layout?
Clearspace product video shows it, http://www.jivesoftware.com/products/clearspace/features/videos.jsp.
You'll get the "customize" link on the Overview tab when you log in as an administrator.
"Operations: customize" in this case is just the page saying "<space_name>: customize". So if you had a "Personnel" space, it would say "Personnel: customize".