Open the note from the list, then:
- Edit opens the form (Edit Note). Change anything and tap Save. Changing the date or time sets its reminder again.
- Delete removes the note with its photos, videos and voice memos, and cancels its reminder.
Deleted notes can't be brought back; there's no trash. If you might need it again, share it somewhere first.
Notes set to expire delete themselves (see "Notes that expire after 2 or 7 days").