[root@localhost ~]# yum install phpmyadmin

This will install it in /usr/share/phpmyadmin

Now, configure it by editing config.inc.php

[root@localhost html]# gedit /usr/share/phpmyadmin/config.inc.php 

add the blowfish secret,
$cfg['blowfish_secret'] = 'a8b7dafdferHJHJ^&U^45776TIUuiYc6d';

and i also changed to mysqli in,
$cfg['Servers'][$i]['extension'] = 'mysqli';

Now you could access the phpMyAdmin by,
http://127.0.0.1/phpmyadmin/

This is possible because an alias is created for apache to the directory where phpMyAdmin in installed [ie /usr/share/phpmyadmin]. This is done in the file,

[tony@localhost ~]$ gedit /etc/httpd/conf.d/phpmyadmin.conf

You will see a lines like,
Alias /phpmyadmin /usr/share/phpmyadmin
Alias /phpMyAdmin /usr/share/phpmyadmin
Alias /mysqladmin /usr/share/phpmyadmin


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You could also install phpMyAdmin manually by downloading phpMyAdmin.
Make sure you download the version 2.xx and not 3.xx[requires PHP 5.2] as Cent OS 5.3 has only PHP 5.1 by default

Extract the tar.gz file to your desktop.

Copy it to /var/www/html/phpmyadmin as root,

[root@localhost ~]# mv /home/tony/Desktop/phpMyAdmin-3.2.1-all-languages /var/www/html/phpmyadmin

Give the appropriate permission for apache,
Set owner as apache

[root@localhost html]# chown apache -R /var/www/html/phpmyadmin/

Set the group owner as your user, this is good as you can edit the files easily,

[root@localhost html]# chgrp tony -R /var/www/html/phpmyadmin/

Now give group user the write permission

[root@localhost html]# chmod g+w -R /var/www/html/phpmyadmin/

Now, add the blowfish secret and mysqli extension as above,

Thats all.