You have to use Alias directive in certain virtual host config:
<VirtualHost domain.com>
...
Alias /phpmyadmin /hsphere/shared/apache/htdocs/phpMyAdmin
...
</VirtualHost>
(PhpMyAdmin is installed in /hsphere/shared/apache/htdocs/phpMyAdmin directory)
Then you can access it by
http://domain.com/phpmyadmin
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