how to sync D80 and flash unit

[dhlam]

Hey I have a D80 and a generic flash unit that came with my camera
it might be that this unit is not compatible? or i just don't have the
right settings on the camera on.

Anyways let me know if there a setting I need to have to get the flash unit on the horseshoe of the camera to fire. I have the unit on normal mode (there is off/normal/slave) and I'm trying to fire the external flash without firing the internal flash with the D80 in manual mode.

Thanks guys