int sensorPin = 30;
int counter = 0;
#include <LiquidCrystal_I2C.h>

#include  <Wire.h>


const int rs = 12, en = 11, d4 = 5, d5 = 4, d6 = 3, d7 = 2; 
LiquidCrystal_I2C lcd(0x27,  16, 2);


void setup() 
{
  // setup serial - diagnostics - port
  Serial.begin(9600);
  pinMode(sensorPin, INPUT_PULLUP);
  lcd.begin(16,2);
   //initialize lcd screen
  lcd.init();
  // turn on the backlight
  lcd.backlight();
}


void loop() 
{
  counter++;
  int sensorValue = digitalRead(sensorPin);
  Serial.print(counter);
  Serial.print(" ");
  Serial.println(sensorValue);
  delay(250);


  if(sensorValue == 0){
    lcd.setCursor(0,1);
    lcd.print("seat 1 needs help");
    delay(5000);
    lcd.setCursor(0,1);
    lcd.print("                        ");
  }
}

3.3v or 5v on Mega Arduino Board to VCC on LCD Screen

GND on Mega Arduino Board to GND on LCD Screen

SCL on Mega Arduino Board to SCL on LCD Screen

SDA on Mega Arduino Board to SDA on LCD Screen

Hall Effect Sensor GND to Mega Arduino Board GND

Hall Effect Sensor +VCC to Mega Arduino Board 5V

Hall Effect Sensor Output to any digital pin on Mega Arduino Board (Use pin 30 if you don't want to have to change the code)

Put Resistor through output pin and 5V pin (10k Resistor)