Hi Steven,
From your post, I understand you would like to know whether you can skip “point Name Servers” process so that you can add a new domain to work with Office 365 service.
In terms of you cannot press” Done, go check”, it is suggested that you skip “Change name servers” step, press Cancel directly. You needn’t be worry about the process has not been complete. You will continue to add the domain whenever you access the Admin page.
In addition, this online site provides many helpful guides for setting up Office 365. If you have any questions when using Office 365, it’s always our pleasure to be of assistance.onlinehelp.microsoft.com/.../office365-smallbusinesses
Thanks,
Maggie Li