The original gameGrid looks like this
[[' ',' ',' '],
[' ',' ',' '],
[' ',' ',' ']]
You 're right about the append method. We shouldn't use it because we do not want to add more elements to the end of the list.
We do not use insert either because we do not want to add more elements.
What we want to do is to change the value of the element of the list. Specifically, change the blank element to 'X' or 'O'. In order to do so, you just have to do something like this
gameGrid[index][index] = the value what want to change to ('X' or 'O')