hi guys, i'm using google translator so i do not think you'll understand a lot of what i will say.
I'm doing a project, semaphore with a photoresistor (to simulate nighttime operation).
I already did the sketch but unfortunately I do not read the photoresist correctly.
do you have a sketch already done?

const byte analogInPin = A0;  // Analog input pin that the potentiometer is attached to

void setup() {
  // initialize serial communications at 9600 bps:

void loop() {
  Serial.print("sensor = ");
  // wait 2 milliseconds before the next loop for the analog-to-digital
  // converter to settle after the last reading:

If your photoresistor is connected to a different analog pin you just need to change the definition of analogInPin.

Post your sketch with detailed description of what goes wrong, and what it should do, and we can have a look.

By the way, this probably belongs in project guidance or maybe sensors - this board is more for the paid jobs.

Are you not reading the photoresistor correctly, or are you not getting the values you expect?

What values are you getting? What are you expecting? Which photoresistor are you using? How is it connected? You do have a fixed resistor in series with the photoresistor, right?