You generally click on topic in TOC (lower) that is only one level deep here - remember, it's just "Getting Started". We'll do our best to provide navigation between "chapters" as well (later). For the moment you have to get back here and click on the next chapter you're interested in by yourself. You can find Getting Started links (chapters and this index) in top navigation menu as well.
If you'll find this Getting started too long you should check How To Build a Simple Cube Map which is definitely the simplest all-round cook book for the UT3 level with result as simple as possible while still playable.