The 'out-of -the-box' OpenForum page templates display a menu on the left of the page. This menu is defined on the page /OpenForum/LeftMenu. The menu list of pages is defined by creating a bulleted list of page links for example:
Sub options can be defined as second level bullet points for example:
The /OpenForum/LeftMenu page displays the lists as with any page, but when included in a page template, the style sheet(css) classes used make the bullet links display as buttons.