Should you ever need to change or update a custom segment, follow the below steps, after logging into activeworks.active.com:

Steps:
  1. Click PEOPLE
  2. Click Custom segment tab
  3. Click custom segment name 
  4. Update filter condition(s)
  5. Click search
  6. Click Save as custom segment
  7. Select update custom segment
  8. Click save
Note: To save your updates as a new segment - instead of replacing the old segment - select save as new custom segment on step 7