You mean the library OscP5? It can handle the OSC events sent from Osculator, which communicates with the Wiimote.
At first you should have a look at the OSCulator documentation here.
It's working like this:
1) Connect Wii to OSCulator
2) Set the Proper OUT Port in OSCulator
3) Setup the OSC-out connection in OSCUlator. You can either send MIDI or OSC (maybe even more) - you need to specify this for every button or load a template
3) In Processing start the OscP5 Sender-Receiver example. There you should put in the output port of OSCulator.
If you get a message there, you can go further...
Good luck!