Download? It should come with the Nightly builds. If you click on the File menu you should see Export... and well... that's the one you're looking for.
In case you're compiling Code::Blocks for Linux, the Source Exporter plugin is part of the contrib plugins, so you should enable it through configure, or just compile it later (check the instructions to enable the contrib plugins).
You didn't say the version you're using either. IIRC RC2 didn't have that plugin... but maybe I'm wrong. It's been a long time since RC2 was released.
