You can change your new Squarespace Domain name within five days of registration. This involves starting over: cancelling the domain you just registered and replacing it with a new domain name. After five days, your domain name is permanent and can't be renamed.
Before you begin
A primary domain can't be removed. Your primary domain is the domain that always appears in your visitors' address bar and has a Primary label next to it in the Domains panel.
If you want to remove your primary domain, first set a different domain as the primary domain. You can always change this later.
Step 1 - Open the Domains panel
In the Home Menu, click Settings, and then click Domains.
You can also press the ? key while any panel is open and search domains.
Click the domain you'd like to change.
Step 2 - Cancel the domain
Scroll down and click Cancel Domain.
Step 3 - Register a new domain
If you cancel the domain within five days of registration, you’ll receive a refund, and the domain will no longer point to your site. A domain can’t be cancelled after this five-day grace period.
To replace the domain, register a new one.