Before you get started, please read the excellent TYPO3 Getting Started Manual or download the PDF Version (3.9MB). Make sure you read the sections 'General principles', 'Edit and create pages and content', 'Special content elements' and 'Image archives'.
If you know German, there's also the Handbuch für Redakteure (sorry, no English version available yet).
For the curious, here is the full documentation overview for TYPO3.
The TYPO3 team has also prepared over a 100 short video tutorials. You can get them for both Windows and non-Windows codecs here.
We have started adding blender3d.org specific documentation to this section. The following pages are available: