Unfortunately, planned TrainerRoad activities cannot be exported to TrainingPeaks.
However, your completed TrainerRoad activities will be able to sync with TrainingPeaks. You can set up an automatic sync between TrainerRoad and TrainingPeaks in your Ride Sync settings. Learn how that's done here:
You'll also be able to sync your planned TrainerRoad activities to an outside Calendar Service like iCal and Google Calendar. Read more about that here: