how to create demo page [theme wordpress]

I create free theme wordpress website but i don't know how to create
demo page of theme wordpress

like this
V
V
Demo
http://wptemplates.org/go.php?http://demo.camelgraph.com/lombardia

Download
http://wptemplates.org/go.php?http://camelgraph.com/wp-content/plugins/download-monitor/download.php?id=40

thank you for every answer

i've never designed a wp theme before, but god knows i've seen/downloaded/purchased my fair share of them.

from what it looks like - when people make demo sites it appears to just be a subdomain populated with miscellaneous content. shouldnt be too difficult.

It is generally just a subdomain. While the links you give are on wordpress.org, the demos themselves sit on other servers, ostensibly set up and run by the theme's creators.

For a cheap win, get a .info domain for $0.99c and then 'host' the demo on one of the many sites that offer free WP hosting.

thank you for your answer