//int temperatureArray[5]; // the number in the brackets is the size (five elements in the array)
int temperatureArray[5] = {23,24,56,12,40}; //array is now initialised 
//could have initialised all the vallues of the array to 0 by doing this {0}
void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  Serial.println(temperatureArray[1]); //you can index the number you want from the array
  //remember that in coding indexing starts from 0
  //to modify a value in the array
  temperatureArray[1] = 30;//changes the value at index 1 to 30
  Serial.println(temperatureArray[1]); 

  for (int i = 0; i<5; i++){
    Serial.println(temperatureArray[i]);
  }
}

void loop() {
  // put your main code here, to run repeatedly:

}