You can change the name servers of your domain name via the Domain Name Management Area at http://www.pickaweb.co.uk/cgi-bin/manage.cgi

If you cannot remember your username and password please enter your domain name without www at http://www.pickaweb.co.uk/getpassword.html and details will be emailed to you straight away.

Please check this tutorial on how to change the DNS http://www.pickaweb.co.uk/movies1/managedomain.htm