You probably set up the retrospective without those people involved. This option is available when triggering a retrospective meeting via the management interface of Team O'clock.
To fix that you can simply invite the users of interest using the + option on the header of the retrospective meeting next to your avatar.
Hover the note you are interested in, to see the Edit link
Click Edit and change your note in the note input
To change the board area for the note, drag and drop the note to the appropriate column
To delete a note, edit it remove the text content and press enter
To switch the area that a note belongs to, drag the note and drop it to the appropriate column.
The easiest thing to do is to group similar notes. To do that drag one note on top of another. Grouped notes have a parent note that will take all votes and "represent" the group during the discussion stage.
If your team agrees to keep only one of the notes you can delete all other notes that are duplicates. To do so:
Hover each note and click the Edit link displayed on the rightmost side of the note
On the input, remove the content of the note and press enter
If you can't see the Edit option when hovering over the note, the retrospective is at the Discussion or Voting step.
To edit a note:
Go back to the Group step
Edit notes as described above