Only the creator of the goal, manager, or Admin can edit or add Milestones or Check-Ins.
To edit a goal you must first go to the Goals tab and select the specific goal.
From there you will need to select the Pencil icon located near the bottom right hand corner of the goal.
The "Set A Goal" pop-up window will display. You can make your edits within this window. When you have made your edits, click SAVE.
Video Instructions: http://screencast.com/t/4xLrvo1ihbG