Google sticks with it’s idea of making domain management simple with it’s quick and easy dns editor.
Select DNS from the left menu.
In the Nameservers screen click on the Use custom nameservers radio button.
Enter your custom nameservers in the text boxes. To add additional namerservers click the + button on the right side of the text box.
When you’ve entered all your nameservers click Save.
You can edit your dns at any time by coming back to the screen, pressing Edit and updating the nameservers in the textboxes.
It can take a while for domain name servers to update. A lot of companies say it can take up to 24 hours but I’ve found that in most cases it takes anywhere from a few minutes to a few hours.
Your browsers cache can prevent your page from loading properly when the DNS has updated so either clear your cache or check with a different browser/device if you think the changes might have taken affect.