The fan/light combo is intended to be controlled by three switches, however this isn't entirely necessary. The easiest way to deal with this without running any additional wires would be to wire nut together the fan and the light to the black lead from the switch and then just wire nut together the neutral. The night light in this instance will not really have a meaningful function as the primary light will always outshine it, so you can just cap that off with a wire nut.
The consequences of the above is that when you turn on your light, you will also be switching on your fan at the same time.
If you don't wish for the above then the other option is to run 12/4 (20A circuit) or 14/4 (15A circuit) from the switch to the overhead fan/light box. This isn't too bad if you are in the middle of a remodel and there is no drywall up, or if your bathroom is on the second level and you have access to the attic. Simply dropping the line down from the attic is possible if there is no insulation in side of the walls to get in your way. If neither of these are your case then running the new wire from the switch box to the fan box will probably involve you cutting drywall in your bathroom ceiling.
Once you have properly dropped the new wire in place, you can use each individual colored wire from its own switch, and have the black hot wire from the circuit breaker wire nutted to all of the colored wires in the switch box.