You have two options to install Wordpress in Ubuntu 9.10. The first option is to download and install Wordpress manually. If you are in a shared web hosting environment, you have to do this way.
The second option is to install it from the Ubuntu's repository. If you are the root, you can just type:
apt-get install wordpress
Everything will be installed and configured automatically for you.
However, you need to change following configuration manually, otherwise the Wordpress can only be visited at your local host, like http://localhost/wordpress/. If you visit it from network, like http://your_ip_address/wordpress, you will get an error.
You can solve it as following:
sudo cp config-localhost.php config-newhostname.php
sudo chown www-data config-newhostname.php