How to Customize your Wiki's Sidebar

You can customize your Wiki's sidebar by editing the MediaWiki page MediaWiki:Sidebar.

Section headers

The Section headers you can see in the image to the left are created by adding * Name of section header to the MediaWiki sidebar page.

Links
Both internal and external links can be created by adding ** Page to link to or URL of an external siteLink to display.

Customizing your Sidebar further (Slightly more advanced)

There's an extension you can install on your Wiki that allows you to customize your Wiki's sidebar further on a per-page basis. Click here to go to the extension's page on MediaWiki.org