http://support.godaddy.com/help/article/664/setting-nameservers-for-your-domain-names
Click on “Setting Nameservers for a Domain Name Registered with Us”
Step 1: Log in to your Account Manager.
Step 2: Next to Domains, click Launch.
Step 3: Select the domain name(s) you want to modify.
Step 4: From (Nameservers), select Set Nameservers.
Step 5: Select one of the following:
“I have specific nameservers for my domains”
Please enter the following nameservers
Nameserver 1: NS1.IXDNS.COM
Nameserver 2: NS2.IXDNS.COM
Step 6: Skip This Step
Step 7: Click OK.