Users and Passwordds are stored in conf/users.auth/php . To change the password, the md5sum needs to be altered for the user within this file:

echo -n "password" | md5sum    # Use the output to replace the users password hash

Firstly, forget the yum repos version of DokuWiki, its a crippled piece of shit.

cd /var/www/html
wget http://www.splitbrain.org/_media/projects/dokuwiki/dokuwiki-2009-02-14b.tgz
mv dokuwiki-2009-02-14 wiki
rm dokuwiki-2009-02-14b.tgz
 
chown -R apache.apache wiki
chmod -R 775 wiki

goto http://host.wiki/install.sh

Enter in the details the best way you know how, then delete the install.php.

This method is a shit-tonne easier to install then the yum way (fuck you yum!!)