I'm assuming you have the arcade output with a molex 6 pin connector (betson has models with ps/2 output, which would just plug in like a normal mouse).
Don't worry about the schematic near the top of the page; that's the insides of the trackball. It's fun to know if you're into the "why" in eletronics, but not really needed by people who just want things to work. Go down to the part titled with "Molex Connector Wiring", and wire as noted.