There are two areas where you can store notes within a game.
 
The first area is in the message box that may be used to communicate with an opponent (for example to type things such as 'Hello, enjoy the game'). In this case you can use hidden comments . This may be done at each move, as desired. It cannot be done when it is not your turn. It cannot be done after a game has finished. To read your notes through completely would require you to go back to the first move at which moves were made, and then move the game forward move by move. This can be useful when reviewing a game.
 
The second area is on the game page for one of your running or finished games. There is a private game note section, where you can enter notes about your game. Those notes are only visible by you. You can make or change notes in this area when it is your turn, when it is not your turn, and when the game is finished. On the game page there is a button "Show notes" to make the notes visible for you. Hiding the notes does not delete them. They simply do not appear on the screen. When the note section is hidden you are not able to create or change your notes in that area. After making or changing your notes they can be stored with with the "Save notes" button. If you do not do this your notes will not be saved. Making a move and submitting it does not automatically store new or changed notes.
 
If there is no button "Show notes", you must first activate game notes in your user profile by unchecking the
"Hidden" checkboxes for the board sizes of your choice. Other settings around the game notes are about the place for notes (right of the goban or below it) and the screen size of the note area. The width and height are only for display. They don't restrict the number of characters of your notes.