Log onto your account.
On your Dashboard, click on ‘Domains’.
Find the domain you would like to switch nameservers for and click on the three dots to the right of it.
From the list of options, click on ‘Manage Nameservers’.
Click on 'Use Custom Nameservers' and fill in the nameservers you would like to change your domain to.
Once the new nameservers are filled in, click 'Change Nameservers'.