How do I customize my CMS?

Most of the tutorials can be found in your CMS pre-built content already. They are not dummy content. You may un-publish them when your site go live.

Administer > Content management > Content

or 

visit your target content and click "Edit" on the tab bar, learn from the source code by switching to HTML Source in the WYSIWYG (What-you-see-is-what-you-get) editor.