If you've registered a domain name, then your website isn't published immediately. If your website hasn't been published yet, you'll see a green Publish button in the top right corner. Click on this button to publish your website on a public website address. After your website is published, changes you make are immediately reflected on your website.
⚠ Warning: You can only publish your website once. After that, any changes you make will automatically be shown on your live website. To avoid this, use Offline mode for website maintenance.