NETTUTS.com has posted what they consider everything you'll need to get started with the CodeIgniter PHP framework:

CodeIgniter is a web application framework for PHP. It enables developers to build web applications faster, and it offers many helpful code libraries and helpers which speed up tedious tasks in PHP. CodeIgniter is based on a modular design; meaning that you can implement specific libraries at your discretion - which adds to the speed of the framework. This tutorial will attempt to show you the basics of setting up the framework, including how to build a basic hello world application that uses the MVC approach.

They start by looking at why you would even use a framework, what CodeIgniter is and what the MVC design pattern is (including its flow). The rest of the tutorial is broken out into the "Getting Started" guide:

• Downloading CodeIgniter
• Installing and Exploring CodeIgniter
• Configuring CodeIgniter
• Testing CodeIgniter
• Configuring CodeIgniter Cont.
• Create the Helloworld Database
• Create the Helloworld Model
• Create the Helloworld Controller
• Create the Helloworld View
• Ta-da and Some Extras