We at Constellix are not a domain registrar. However, our sister company Domains Made Easy is so we will be using them as an example. First off, you want to go to your registrar’s website. On that site, you are going to want to go to your account.
Once you are signed in, you are going to want to select the “My products” option to show your domains. You will then select the “DNS” option within the domain that you would like to edit. On the DNS Page you will see a Nameservers section. You will want to click the dropdown and select the Custom option. Once custom is selected, you will then be able to enter the name servers that we assigned you (these can be found within the Name Servers tab within the domain). Below is an example of one of our name server sets entered. Once these are saved, your registrar should push the update to the registry and the Top Level Domain name servers so that you will now be resolving to our name servers.