After installing Ubuntu on a PC,  you need to add these packages:

Apache2 - this is the actual web file server

sudo apt-get install apache2

Configure apache2  

PHP - popular web scripting language

 sudo apt-get install php5-mysql

MysSQL - the database

sudo apt-get install mysql-server

To create a new database, use the mysqladmin command:

mysqladmin create [database name]

 

Set up Joomla:

http://www.basicconfig.com/linuxsoftware/howto-setup-joomla-ubuntu