If you would like to update your domain contact information, you'll need the registrar username and password assigned to the domain. If you don't know the username and password then contact support for assistance. Once you have the username and password go to the registrar portal at:

https://reliablepenguin.com/domains/

You'll see a login form where you can enter the domain name, username and password. When complete click the Manage Domain button. 

After login you can click the "Organization", "Admin", "Billing" or "Technical" items on the top menu to update the associated information.