To modify the contact details (excluding the organisation name field), just follow these simple steps:

1. Click on the "Client Login" link at the top of this page
2. Type in your email address and password and click Login
3. Click on the next icon on the domain you wish to update, or tick multiple to bulk update domains
4. Scroll to the bottom of the page, and click "Contact Information" under the Management heading
5. You can modify each of the four domain contacts (Registrant, Admin, Tech & Billing) by Modifying the Details under the relevant contact
6. Type your new details, then click Save Changes