To edit your name servers you start by loggin in to your Customer Area (Not the cPanel).
You can access the customer area with the following link, https://billing.gethosting.ie, the login details was sent to you when you signed up for GetDomains. If you have forgotten your login details or lost the email just use the "Forgot Password" link in on the page.
Once you have your username and password simple login to the page, after that do the following:
Click on Domains > Click the icon "Handle Domain" to the right in the list of your domains > Click the tab called "Name Servers". In here you can manually change your name servers for the domain you wish to manage.