Did you install PhpMyAdmin via apt?
Have you created a symlink? If not you will need to do the following
Code:
sudo ln -s /usr/share/phpmyadmin /usr/share/nginx/html
Your php will also need mcrypt enabled.
Restart php and nginx for good measure and you should be able to load it from
http://yourdomain/phpmyadmin
And remember to lock it down to your IP or VPN if possible