the Godaddy changed their Domain manager appearance in 2013 so it now works different way.

Login to GoDaddy > Domain Manager > CLick your domain name > scroll down and find "Hostnames"
..then add new one there. If it dont works, check that your domain is not pointed to godaddy.

Example inputs:
ns1 (you hosting server rip)

Once nameservers are registered like: ns1.yourdomain.com and you added IP of your server, you may need to wait like 15 minutes once change is applied, check http://intodns.com to see when change is made. Then edit your hosting server DNS configuration.