To edit the links in your MediaWiki sidebar, you should log in as admin and edit the MediaWiki:Sidebar page.

The format of the link items is:

** link target|link text

The link target can be the name of an interface message, a wiki page or an external link. The link text can be the name of an interface message or plain text.

For example, if you wish to edit the Help link by changing the text from Help to Support and pointing the link to www.siteground.com, you should edit the MediaWiki:Sidebar page and change:

** helppage|help

to

** http://www.siteground.com|Support

For more information on how to customize your MediaWiki sidebar, please check the official documentation.