Create a link in /var/www like this:
sudo ln -s /usr/share/phpmyadmin /var/www/
Note: since 14.04 you may want to use /var/www/html/ instead of /var/www/ (same for php 5)
If thats not working for you, you need to include phpmyadmin inside apache configuration.
Open apache.conf using your favorite editor, mine is vim 🙂
sudo vim /etc/apache2/apache2.conf
Then add the following line: