Now that you have the WA Nameservers, you can proceed to visit 123-reg.co.uk and log in to your account.
From your Control Panel, make sure that the domain name you want to update is selected from the dropdown menu next to the word Domains.
You can then click on the green button labelled MANAGE
From the Management page of your domain name, you can scroll down to the Advanced domain settings, where you can then click on Change Nameservers (DNS).
From the Nameserver Management page, you can remove all entries from the four (4) nameserver fields, along with adding the two (2) nameservers that you made a note of previously.
You will want to ensure that there are no spaces before or after the nameservers you have added, and also make sure that there is no dot (.) at the end of the nameservers.
Once you have added them both, you can click on the Update button to apply the changes.
DNS changes can take up to 72 hours, however, usually no more than 24 hours and as long as you haven't viewed the website in your browser within the last 24 hours, the change usually only takes a few minutes.
You can now click on the Next Page button below to go to the next step.