The pages under “Learning” (http://fritzing.org/learning/full_reference) seem to be grossly out of date. The images and sections don’t match what I see in release 0.9.3b on Linux.
What is the “Code” window?
How do I install other platforms and boards?
The code window is a work in progress. I don’t think the arduino one can load code as it was waiting for an arduino ide update and hasn’t been updated. The Picaxe version (which I haven’t used) is I think the only one that is fully functional.