Does my motor need a second capacitor?
Why does my motor only have one capacitor? All the others seem to have
  two?


You probably mean: Why this motor has only one capacitor, while other saw motors have two?

A: Because the saw operates also in no-load condition, while this motor is intended to be start and run with load always present. Motors with two capacitors have one start and one run capacitor. The start capacitor is disconnected when motor reaches certain amount of speed by centrifugal switch, which your motor doesn't have. Running this motor as saw is not recommended as the capacitor would blow sooner or latter.


  where do I put the neutral and live wires?


On connection marked as LINE, while the PE wires goes to the earth mark.


  Why does it have a circuit breaker?


Probably is the thermal switch, for overload protection. 

The circuit breaker has to be installed on the supply side, that's where the connecting cable comes from.