It's automatic, not need for any additional configuration or administration. For example:

• http://www.dorfwiki.org/wiki.cgi?FrontPage -- the base page
• http://www.dorfwiki.org/wiki.cgi?FrontPage/Context -- configured as an English subwiki
• http://www.dorfwiki.org/wiki.cgi?FrontPage/RecentChanges -- automatically offered in the link bar from all subwiki pages