I have PFPX so it sets my waypoints, SIDS and STARS automatically.  I want to use the ATC in FSX but I don't know about how to put the waypoints in the fsx flight planner.  I know you can drag the line to get the waypoint to be added but what if I don't know where the waypoints are on the map.  I have been creating an IFR plan 50 miles out from the airport to have ATC give me vectors for landing but I would like to have ATC guide me like real life throughout the entire flight.  I was flying from Tampa to Frankfurt Germany which makes it hard to put in waypoints in FSX when it is crossing the ocean.  Any help or suggestions?

If you export your PFPX plan in FSX format, the flight planner will read it and therefore knows about the waypoints. I think those then enter the FSX plan as coordinates plus a waypoint name. Now don't ask me how the inbuilt ATC considers those special names, but the routing itself should fit.

I know how to export the flightplan to PMDG to have it automatically input into the aircraft's FMC.  If I am understanding you correctly if I am able to export to the FSX format when I go to flight planner in FSX it should automatically load?  I am assuming I would just hit the load button and find the file.  How to do I export to FSX format or is it automatic? Thanks.

In PFPX, just use the "Export" dialogue with that huge list of supported addons and formats. Once PFPX knows your FSX folder and the one of the own documents, it should populate that list with a "Microsoft Flight Simulator X" entry aiming for Flight Simulator X Files, which happens to be the default path for all flight plans.

 

Check this list entry and click save.

 

Once you are in FSX, open the Flight Planner and perform the steps you've mentioned:

I am assuming I would just hit the load button and find the file.

The exported flight plan should be right there, having the ICAO codes of the airports involved as name. Once you succeed, the FSX flight planner will show the corresponding airports and also draw the PFPX route on the map.

 

As said, I don't know if the ingame ATC can handle all the waypoints by name, but the sheer coordinates should be available.