Using the starting Kit I find a programming sentence that does not work. Please help
It should be
buttons[0] = 2; //set the first element of the buttons array to 2
otherwise you are trying to declare the array for a second time and to make it worse the second one would have zero elements
In future please post your code here and not a picture of it and use code tags when you post it.
Those two lines that mention buttons are not part of the sketch, but a broken example of using arrays.
Remove them.