MediaWiki V.1.30.0
MediaWikiChat V.2.18
1.Download all files and place them to extensions/MediaWikiChat
2.Add "wfLoadExtension( 'MediaWikiChat' );" at the bottom of LocalSettings.php
3.Go to Your_wiki/mw-config and update your MediaWiki (That will automatically create the necessary database tables that this extension needs. )
4.Add "$wgChatMeCommand = true;" below the line of installing MediaWikiChat
But it doesn't work
P.S. I had to update MediaWiki two times because the first time necessary database tables weren't created