How Do I customize default page

All themes are customizable but you have to have some knowledge of CSS, HTML and PHP.

If you have Firefox, get Firebug. It will allow you to alter the HTML & CSS and see the changes without committing them to your site. That’s a good way to learn what does what without breaking anything.

Try using http://starkerstheme.com/ as a starting point – it’s basically just a blank canvas with all the functionality done for you.