PID temperature control

thanks for the reply.I did try to combine with code above.I got something like this

#include <Wire.h> 
#include <LiquidCrystal_I2C.h>
//I2C pins declaration

#include <PID_v1.h>
LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE); 

double Setpoint, Input, Output;

//Specify the links and initial tuning parameters
PID myPID(&Input, &Output, &Setpoint, 8.8, 1.4, 2.3, REVERSE);
int tempPin = A1;   // analog input to read the temperature
int temp;

int set = 15;           //set temperature variable
int lastset = 2;
int Counter1 = 0;       // counter for the number of button presses
int Counter2 = 0;       // counter for the number of button presses
int State1 = 0;         // current state of the button
int State2 = 0;         // current state of the button
int lastState1 = 0;     // previous state of the button
int lastState2 = 0;
int val = 0;
const int set1 = 11;     //temp up and temp down buttons
const int set2 = 12;

int pwm1 = 9;        // pin ENA on L298N
int in_1 = 1;        // in 1
int in_2 = 8;       // in 2

int pwm2 = 10;        // pin ENB on L298N
int in_3 = 6;          // in 3
int in_4 = 7;          // in 4



void setup() {
                                                           

  pinMode(set1, INPUT);
  pinMode(set2, INPUT);

  Input = analogRead(tempPin);
  Setpoint = 15;
  myPID.SetMode(AUTOMATIC);
  myPID.SetSampleTime(200); 
  
  lcd.begin(16,2);  
   
  
 }
                           
  void loop() {
 int temp = ((5.0/1024.0) * analogRead(A1)) * 100;  //10mV per degree 0.01V/C. Scalling
 lcd.setCursor(0,0);
 lcd.print("Temperature:");
  lcd.print(temp);
      
State1 = digitalRead(set1);
  State2 = digitalRead(set2);  
  if (State1 != lastState1) {
        if (State1 == HIGH && set!= 15) {        //if up button is pressed, add 1 to des
        set++;
     } 
    
  }
  
  if (State2 != lastState2) {  //if down button is pressed, subtract 1 from des
       if (State2 == HIGH && set!=5) {
       set--; 
    }
   
  }
   myPID.Compute();
  analogWrite(3, Output);
  lcd.setCursor(0,1);
  lcd.print("Set Point:");
  lcd.print(set);
  lcd.print("C   ");
}