I could not find any reference to Pd extended on that page.
I guess you mean this http://puredata.info/docs/StartHere/
they probably have not updated their wiki after discontinuing extended.
Just download Pd 0.46 http://puredata.info/downloads/pure-data/releases/0.46-7 and follow the guide here http://en.flossmanuals.net/pure-data/ .
Note that some of the externals provided by Extended are nothing but abstractions (that is: they are Pd patches in themselves). To identify them, right click on the object and if the "open" menu entry is available, then it means they are abstractions. These can be easily re-used with vanilla and with Bela by simply copying the source file in your project folder.