I don't even know where your departure airport is located. In general, if you are departing from an uncontrolled airport, you can use the PF3 Display utility to see the available frequencies for the airport. Use the FSS frequency (or 122.2 by default, if there is none) to open your flight plan, then use an advisory frequency (Unicom or Multicom) to announce your intentions to take the runway. Once airborne tune the Departure frequency listed in the Display utility and press 0 to make contact.
EDIT: The PF3 Display Utility will work only when PF3 is connected, so Thomas provided a suggestion to check the facility frequencies before you start your flight or connect PF3. See below: