| First, you cannot use a dimmer switch. A light dimmer switch will damage the fan motor. You can use a wall mounted fan switch.
Exactly what you will have to do depends on how your house wiring is currently done.
In the first drawing, the power is brought to the wall switch. The neutral wire just passes thru the box and goes to the fan/light. The wire for the light goes thru the switch. Another wire is connected to the incoming hot and goes to the ceiling box where it is connected to the fan motor wiring.
In the second drawing, the house wiring brings the power to the ceiling box. The neutral is connected to the neutral of the fan/light. The incoming hot is connected to the fan motor wiring and to one of the wires going to the switch (should be the white). The power goes to the switch on one wire and comes back (when the switch is on) on the other. That wire is connected to the light wiring of the fan/light.
If your current house wiring is as drawing one you will only have to add the switch.
If your house wiring is as drawing two you will have to replace the existing wiring between the switch and the ceiling box with 3 conductor cable. You would use one wire of the 3 conductor cable to go to the switches. You would use one wire to come from one switch to the light, and one wire from the other switch to the fan . | 
Linear Mode
