It's not currently possible to edit a custom domain name through the app. What you'll need to do is first cancel your subscription through iTunes here:

After you cancel your subscription, create a new site and re-subscribe with the correct domain name. Let me know if you need any additional help!

If you want to use your old site with the new domain, please send us a message through the app or via email with the old domain name and the new one you would like to connect the site to.

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