As the Account Owner, you can edit stages by navigating to the Admin > Stages screen.
On this screen you can rename and reorder stages. You can also add new stages or delete stages you no longer need.
To rename a stage, click the edit icon next to a stage, to delete a stage click the delete icon:
If you want to reorder the stages, drag a stage using the grip icon to the left of the stage and drop it somewhere else in the list:
NOTE: The "Lead", "Closed" and "Trash" stages are used by the system, and cannot be renamed or deleted.