Use this page to get used to Squarespace. Try adding blocks and editing text. To learn how to add blocks see this user guides. This page will not appear on your site, but is live on the internet, so you can try anything you wish, and the public won't see it.
What i a content block: http://help.squarespace.com/guides/what-is-a-content-block
Using the Layout Engine: http://help.squarespace.com/guides/building-a-page-with-layout-engine
Moving blocks: http://help.squarespace.com/guides/moving-content-blocks