installing LAMP problem ubuntu 10.10

Hi
I'm using this guide to install Lamp on Ubuntu 10.10 on an Asus 1005PE: http://www.techtickle.com/how-to-setup-lamp-on-ubuntu.html

When I get to the point of "... To test if everything is fine and working , create a test.php file and add any php code for examle-

<?php
echo 'Welcome to TechTickLe';
?>

Now you can open this file by the url http://localhost/test.php in the web browser . It should prompt Welcome to TechTickLe. If not working, then something is wrong with your local server..."

I have no idea what to do. How do I create the test.php file?

Thanks