Completing setup:

To complete installation cd into the MediaWiki install location, but
make sure to start mysql first with:

$ /etc/init.d/mysql start

$ cd /var/www/localhost/htdocs/mediawiki/

The host directory, localhost, may change depending on your installation.

Then temporarily make the MediaWiki /config directory writable
to the  user the web server is running as. The quickest way is 
to make  the directory world writable.  For example:

$ chmod a+w config
 
Then access it, for example:

lynx http://localhost/mediawiki/config/
 
After setup move the newly created LocalSettings.php from the config/
directory to the main mediawiki directory, for example:
  
$ mv config/LocalSettings.php .

    Remember to restore safe permissions to the MediaWiki config/ and
    LocalSettings.php (which contains clear-text passwords).
    chmod a-w config
    chmod ug=r,o=  LocalSettings.php
    chown root:apache LocalSettings.php

After these steps MediaWiki should be accesable at
http://localhost/mediawiki/
 
Enabling Optional Features:

If you wish to enable image uploads then you must manually edit the
LocalSettings.php file to uncomment the \$wgDisableUploads line.  If" 
MediaWiki was built with the imagemagick USE flag the directory
permissions are correct, otherwise you must install ImageMagick and" 
also adjust permissions on the images directory to allow the server
to write.  For example:
 
$ chown apache:apache /var/www/localhost/htdocs/mediawiki/images

If you wish to enable the math support then you must manually edit" 
the LocalSettings.php file to uncomment the \$wgUseTeX line.
Mediawiki must have been built with the tetex USE flag enabled or the
necessary support executable will not be present.