You can link PowerCenter to many third party platforms such as TrainingPeaks, Strava, Today's Plan, etc. These are great platforms to share your activities with friends or your coach.
If you also use your watch platform such as Garmin Connect or Movescount, be aware that those platforms can also connect to TrainingPeaks et al. If you connect both, you will get double entries since TrainingPeaks et al cannot recognize that it is the same activity.
To avoid duplication, connect directly from your watch' platform to your preferred platform.
If you have additional questions, contact firstname.lastname@example.org.