By "12/3", are you referring to a cable with three insulated conductors (black, red, white) and one bare wire? Or do you mean 12/2, with two insulated conductors (black and white) and one bare wire? The latter would make a lot more sense, and I'm going to assume that you really meant 12/2.
Connect all three white wires in the switch box to each other and tuck into the back of the box.
Connect all three bare wires to each other, and to two bare or green pigtails, one to each green screw.
Connect the power cable black wire to two black pigtails, one to a brass screw on each switch.
Connect the black wire from the fan to the remaining brass screw on one switch, and the black wire from the light to the remaining brass screw on the other switch.
Is this enough?
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