You can edit a segment's rules or delete a segment you no longer need.
Step-by-step instructions
Go to Settings.
In the Elsewhere section, click Organisational segments.
Find the segment you want to edit/delete and click the three dots button on the right of its row, then choose:
Edit to change the segment's rules. Make your changes, then click Save changes.
Delete to remove the segment. Click OK to confirm.
Caution: Before deleting a segment, check it isn't needed for user or report filtering, restricting administrator access, Smart Enrolments, or linked Documents & policies.
Note: Deleting a segment doesn't affect the user profile field associated with the segment rule.
If you're setting one up for the first time, see How do I create an organisational segment?