Trouble Getting Sound Out Put In Cubase Sx Options

[The Raz]

I have a powerbook G4 that I am pluging my guitar straight into, i am trying to use cubase to record guitar tracks. the input is being recoginsed but their is no moniter output until after i play back what i recorded, how can i hear what i am recording , i have tried messing with all the stuff on the mixer but still no sound, please help