For Website Builder user need to be registered and logged in on website
Go to Web Development and Management -> Website Builder
You will see two buttons there
By click on Buy now You will see a list of packages for Monthly Website Development
Buy click on Try Now you will go to Website builder page
You will see demo website now because you have not purchase any monthly website development package or package not activated
You can not create new pages for demo website and can not publish to server.
But clicking on Demo Website link you can some already created pages and you can modify existing pages.