Note: In many configurations, once an objective has been confirmed an individual cannot modify their own objective. Your line manager or a moderator can re-open the objective for you which allows you to make modifications.
First, click on an objective to open it. Then open the Options menu on the top right:
Select Change the original objective.
The objective will re-open in draft mode.
Make your changes and save it as draft or confirmed.
The objectives panel will reload showing your changes.