The address of your site can be changed at any time via the Settings tab in the editor. Open up the Settings tab and then click the "Change" button connected to the Site Address.
You have three options when changing your site's address:
The first option is to Use a Subdomain of Weebly.com. This is free and allows you to create an address like myfantasticsite.weebly.com (anythingyouwant.weebly.com).
The second option is to Register a New Domain. There is a cost associated with this as you're registering your own domain name like www.example.com.
The third option is Use a Domain You Already Own. If you've purchased a domain with Weebly you can enter it here. You can also use this option if you bought a domain through another registrar and want to use it with your Weebly site.
Want to use a custom subdomain, like shop.mydomain.com? If you purchased your domain name through Weebly, all you need to do is enter the subdomain address here and it will automatically work when you publish. If you purchased your domain through another company, enter your subdomain and follow the instructions shown after clicking Continue to get that set up at your registrar.