Adding a new comment directly to a cell is extremely easy. Here you will be walked through the process.
Select the cell you wish to add the comment to.
Right click or Ctrl/Cmd Click the cell to open the context menus.
Enter the content you wish to add into the comment field.
Select “Comment” to add the comment to the cell or “Cancel” to cancel adding the comment
You can now see the comment in the Excellentable through a green triangle in the top right corner of the cell.