The key factor is to understand where the power source enters the circuit.
Exhaust fan and light on separate switches.
The power source will either.
Connect two of the black.
Assuming you have 3 wires from the switch box to the fan light location as bill said.
Take the 2 wires on the switch that controls the outlet off the switch twist.
Connect the two white wires in the switch box together with a wire nut.
Then this is what you do.
Attach the red and black wires from the fan light unit to the top terminal screws on the switches.
Light timer switch ul listed fosmon 9 setting 1875w in wall countdown electrical switch off 5 10 15 20 30 min 1 2 4 hr energy saving for fans vent lights heaters decorative 2 pack 4 4 out of 5 stars 166.
How to wire your bathroom so the lights and fan are on separate switches the electrical wiring for separate switching of the bathroom exhaust fan and the light fixture will require identifying.