Installing phpmyadmin for web admin of mysql database.
First install mysql
$sudo apt-get install mysql-server mysql-client php5-mysql
Then install phpmyadmin
$sudo apt-get install phpmyadmin
there is a howto forge document here that gives a fuller explanation.
The correct how to suggests that you include the config file in the main apache2.conf.
Ubuntu/Debian systems have a folder called sites-enabled sites-available in /etc/apache2 .
conf files in these folders are loaded. Generally you will write the .conf files in the available forlder and create soft links to them from the enabled folder. so instead of inlcudeing this line in apache2.conf
I suggest creating a link to it from the enabled folder
ln -s /etc/phpmyadmin/apache.conf /etc/apache2/sites-enabled/phpmyadmin
If doing it properly you should copy it to the sites-available and link to it there, rather than linking directly to it.