Finding your registrar's control panel
When connecting an existing domain, some changes are needed to be made to the settings in the control panel of your registrar (where you purchased your domain from), as detailed in our wizard https://support.wpagency.io/connecting-an-existing-domain
Each registrar is different, the location of its control panel can vary and so can the method of changing DNS records.
Here are some examples of how to locate the control panel in registrars:
1&1
http://faq.1and1.com/domains/domain_admin/dns_settings/9.html
http://faq.1and1.com/domains/domain_admin/dns_settings/index.html
123-reg
http://www.123-reg.co.uk/support/answers/Domains/Web-Forwarding/how-do-i-set-up-my-dns-for-web-forwarding-2526/
Crazydomains
http://www.crazydomains.co.uk/help/dns-hosting/
Gandi
http://wiki.gandi.net/en/dns/zone
GoDaddy
http://support.godaddy.com/help/article/4648/setting-up-dns-using-simple-control-panel
http://support.godaddy.com/help/category/375/dedicated-linux-simple-control-panel-managing-dns
Namecheap
https://www.namecheap.com/support/knowledgebase/article.aspx/1031/2/demo-how-to-set-up-a-cname-record
https://www.namecheap.com/support/knowledgebase/article.aspx/473/2/demo-changing-host-record-settings
Network Solutions
http://www.networksolutions.com/support/how-to-manage-advanced-dns-records/
Register.com
http://www.register.com/customersupport/tutorials/cname.rcmx