First thing is you need to download ubuntu jaunty .iso image from . once you have the .iso image you need to create a bootable CD from this and you need to boot your machine using this CD.
Once It starts booting from CD you should see screen select your language and press enter
Then in next screen you need to select “Install ubuntu” option and press enter
Ubuntu jaunty start installing.
Select your language for ubuntu installation click on forward
Select your keyboad layout in this example i am using united kingdom and click on forward
Now you will See screen with the disks available in your machine here you need to create partitions ,if you want to create manually use the other option you need to click on forward.
Next you need to create User name, password and computer name you can also choose if you want to login automatically or not
List of information available for installation will come you need to click on install to start the installation.
Partitions formating starts.
Installation of ubuntu jaunty to your system starts.
When installation completes you need to restart.
When you restart it will ask for loging and password and thn you can start working on your Ubuntu 9.04.
Hope this will help all the user who are installing Ubuntu for first time.