For the blink practice I followed the instruction on the book and had not too much trouble in understanding.

During the practice I realized I was not familiar with Analog concept and need for variable. (And I was still confused whether it’s C or JS). At first thought it was not working, but later figured out sensor controls the delayValue on the code. Later when I tried differently by connecting to digital input instead, it didn't work.

int sensorPin = A0;    // The potentiometer is connected to analog pin 0                  
int ledPin = 13;      // The LED is connected to digital pin 13
int sensorValue;    //We declare another integer variable to store the value of the potentiometer

void setup() // this function runs once when the sketch starts up
{
    pinMode(ledPin, OUTPUT);
}

void loop() // this function runs repeatedly after setup() finishes
{
    sensorValue = analogRead(sensorPin);    

    digitalWrite(ledPin, HIGH);     // Turn the LED on
    delay(sensorValue);             // Pause for sensorValue in milliseconds
    digitalWrite(ledPin, LOW);      // Turn the LED off
    delay(sensorValue);             // Pause for sensorValue in milliseconds
}