1. Launch and sign in to the app if you have not done so.
2.  While in the app, tap the navigation button.
3. Tap Periods and Goals.
4. Tap on the period you wish to edit.
5. Tap Edit Performance Period.
6. This should launch the performance period editor.
7. Make the necessary edits.
8. When you are done, tap apply.
9. Your performance period list should now be updated with your updated period.