3 way switches, power at fixture, 3 wire (plus ground) cable being routed thru the ceiling box between switches
At the ceiling box - the ungrounded conductor {aka hot} from the fan connects to the black wire from the circuit power supply cable. The ungrounded conductor {aka hot} for the light connects to the black wire coming from the switch 2. The white wire from the circuit power supply cable is the grounded leg conductor {aka neutral} for both the fan and light. This will provide an unswitched ungrounded conductor {aka hot} for the fan and a switched ungrounded conductor {aka hot} for the light.
Bare wires are together and grounded to box (if metallic) and if the fixture has a green wire or a grounding screw , it gets grounded also. Bares and green wires are equipment grounding conductors.
Wrap a piece of black electrical tape around both ends of the white wire going between switch 1 and 2 (and the portion looped thru the ceiling box), as this wire is also being used as a ungrounded conductor {aka hot}.
Be sure to read all documentation that comes with your fan / light combo fixture.
If only switched power required onward then at existing fixture...
If only unswitch power required onward then at existing fixture
Onward power from the switch is not possible with this configuration as there is no grounded leg {aka neutral} available at either of switch locations.

The common screw on a 3 way switch is the odd color screw
If wiring multiple fixtures be sure to check the following guidelines concerning how to do it and what not to do: Wiring Multiple Fixtures.
If you are new at understanding the "politically correct" electrical terminology and need clarification of the terms used, we strongly urge you to read the Clarification of Definitions and Terminology guide. This will explain the terminology used in this article.