The contact form is made possible by the fantastic Contact Form 7 plugin. Once installed and activated, go to its Control Panel (bottom left of the wp-admin dashboard). You can configure the form however you like, or just keep the defaults.
When it’s all set up, copy the shortcode at the top of that page.
Create a new “Page”, and set the Template to “Contact”. Enter a page title, and some optional body text. In the body of the post, PASTE the shortcode that you copied. Publish the page, and you’re done!
If you’re using Version 2.0 or above of this theme (which require WP 3.0 or above), then the Contact Us page will not show in the menu by default. You must go into your “Menus” page and add the Contact Us page to your Main menu and Footer menu.