Publishing
To publish your website, open Hostinger Website Builder and click on the purple Go live button in the top-right:

After publishing your website, you can edit it anytime, multiple times.
It usually takes up to several hours for the domain to completely connect to your website. Until then, you can access your website using an auto-generated preview domain:

Troubleshooting
If after a few hours from publishing your website it is still not showing live, check this article for troubleshooting options.
The most common reason is when the website is in Coming Soon mode, click here to see how to disable it.