Copy the following code, changing the www.example.com to the url for the website you want, and paste in the relevant position on the page where you want to add your preview. Embedded websites usually feature towards the bottom of any given page. For further help with editing pages click here.
++ Website Preview
[[iframe http://www.example.com width="630 px" height="500 px" scrolling="yes" frameborder="1" align="left"]]