If you installed from the extension and not the updater, you'll find a folder of examples in this folder:
[drive]:\Program Files\Multimedia Fusion 2\Examples\Phizix - Chipmunk Engine
They're quite easy to figure out.
You might also try the
Clickteam Support Forum for further help; as far as I know only Dynamite, Chipset, Bloxmaster, and I (the only ones I remember that had good examples) are fairly proficient with the Physics extension. I'm probably wrong, though. (It's almost doubtless that Nifflas would be good at this sort of thing, but I doubt he would have the time and I'm not sure that he uses Chipmunk)